Bits and Pieces Part 6: Rethinking Range and Habitat – Implications

If you’ve been following this series (Part 1, Part 2, Part 3, Part 4, Part 5) you know it has focused primarily on preconceptions about ivorybill range and habitat types and how the actual record paints a very different picture from what many of us think we know about the Ivory-billed Woodpecker. As I noted in the most recent installment, if our knowledge of the Ivory-billed Woodpecker were based on the archaeological record alone, we’d think of it as an upland species. Further, we might very well assume that it ranged from the hills of Georgia, to the Alleghenies in Virginia, to central Ohio and west-central Illinois.*

While it may border on heretical to say so, I think there’s a plausible argument that the ivorybill’s range prior to around 1800 extended as far north as the mid-Atlantic states (New Jersey and Pennsylvania on the Eastern Seaboard) and as far north as central Ohio west of the Appalachians. I’m inclined to think this is likely based on a number of accounts including: Peter Kalm (a student of Linnaeus who reported the species was present in New Jersey and Pennsylvania in the 18th-century), Jefferson (1780s) and Nuttall (1840s) who included Virginia in the range, and Gerard Hopkins a Quaker from Maryland traveling to Indiana to meet with the Miami and Potowatami Nations. Hopkins described a female ivorybill at Piqua, Ohio (north of Dayton, elevation 873′) in 1804 (Leese, 2010.)

In addition, there’s the specimen that Wilson reportedly collected near Winchester, Virginia ca. 1810 (Jackson) and the central Kentucky specimen reportedly collected in the 1780s (Jackson, accepted by Tanner in 1989).

November 2021: Edited to add the Wilson record for Winchester, Virginia is apparently erroneous.

As I see it, the tendency to treat these records as suspect is based, at least in part, on post-Civil War or post-Audubon “knowledge” about the ivorybill and its habitat, rather than anything intrinsically implausible about the claims themselves.

At minimum, one of the Ohio archaeological finds dates to the 15th or 16th century, so there’s strong reason to think that the ivorybill’s range extended that far north at the time of contact. North American Native populations began to decline after Columbus’s arrival, and De Soto’s expedition, 1539-1542,  led to the collapse of the Mississippian culture. (De Soto also introduced the hogs that plague the southern forests to this day.) As a consequence, countless acres of formerly agricultural lands throughout the eastern United States were reforested and remained so into the 18th and 19th centuries. There’s little reason to think that the ivorybill’s range would have contracted at a time when the total acreage of potential habitat was increasing.

I’m reminded that tree girdling may have been an important factor. The only counterargument to the foregoing suggestion about the increase in total acreage after De Soto is that Native American agricultural activity declined drastically during that period, so that while habitat acreage increased, habitat quality may not have. Tree girdling and intentional burning likely played an important role in creating good conditions for ivorybills and could conceivably have led to range expansion during the Mississippian period and again temporarily during the first couple of hundred years of European settlement.

Ivory-billed Woodpecker use of girdled trees was noted by several early observers – notably Audubon, Gosse, and Scott (in Florida, later). While researching this aspect, I came across an interesting account from 1840s Central Louisiana, apparently just south of Alexandria (the citizens of that city are described as “chiefly gamblers or cunning speculators, a nest of incarnate devils, who live by cheating the latest comers, and, whenever possible, each other.”) I’m not aware of this account having found its way into ivorybill literature:

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From Echoes from the Backwoods; or, Scenes of Transatlantic LifeCaptain R.G.A. Levinge (1849).

With this as background, I’d like to propose an alternative explanation (or more accurately an alternative group of explanations) for the ivorybil’s decline. If you think, as I do, that the ivorybill has persisted, this may help explain how the species survived and may even provide some hope for its future, even in this era of mass, anthropogenic extinction.

When it comes to the decline and possible extinction, there has been a tendency to look for one or two causes. The IUCN Species Account gives the following reasons:

Logging and clearance for agriculture are responsible for the dramatic decline in numbers and range. These factors are likely to threaten any remaining population. Hunting has also been implicated in the rapid population decline, and it has been proposed that this was the primary cause of its decline, with habitat destruction playing a secondary role, but this theory is contentious (Snyder 2007, Hill 2008, M. Lammertink in litt. 2012).

Tanner emphasized the importance of logging during the post-Civil War era, although several of his data points seem to suggest that ivorybills were disappearing prior to the most active logging dates. He also stated that the ivorybill’s disappearance “coincided at least roughly with a time of active or rapidly increasing logging.” Elsewhere in the monograph, he focused on food supply, and I suspect that this, rather than logging per se was a more important factor in the ivorybill’s decline.

That’s not to say logging was unimportant; it clearly played a major role. To expand briefly on the point Bill Pulliam raised: by the late 19th century, the more adaptable Pileated Woodpecker, had been extirpated in many parts of its range, and many expected it to ‘go the way of the ivorybill’. That didn’t happen, and PIWOs returned to or became more common in many areas (my own included) as farming gave way to suburban development and forested acreage increased as a result. I’d suggest that for the ivorybill, habitat degradation, rather than habitat loss, was what initiated the decline, with extensive logging and then hunting accelerating an already existing trend.

That is to say, a number of additional anthropogenic factors likely played a role in the ivorybill’s decline and dwindling range, especially outside of Florida, where hunting and collecting likely had much greater impacts than elsewhere. Hasbrouck, writing in the 1890s, contrasted the lack of collecting in Louisiana, Arkansas, Missouri, and Tennessee with what was transpiring in Florida at the time. And it’s important to remember that Florida, which retained ‘frontier’ characteristics far longer than other parts of the eastern United States, was ground zero for the killing and collecting of birds – for commercial and ostensibly ornithological purposes. Ivorybills appear to have been more common in Florida than elsewhere by the second half of the 19th century, but it also seems probable that they were far more heavily persecuted there than anywhere else.

I’m hypothesizing that the shrinking distribution was correlated with settlement patterns in the northeastern part of that range and that by the middle of the 19th-century, east of the Mississippi, it had dwindled to the now familiar outlines, such as those shown on the IUCN range map. Screen Shot 2017-12-22 at 3.42.31 PM

The situation west of the Mississippi is somewhat more ambiguous. A specimen was collected at Forest Park, Missouri (near Saint Louis) in 1886, and there are records from west of the map in Texas dating to the early 20th century. Nevertheless, the general trend toward a shrinking range, which was frequently described in the 19th century literature, is clear.

European settlement brought about numerous changes in the land even before wholesale clearing of forests began.

As mentioned briefly in the discussion of tree girdling, Native Americans used fire for agricultural and wildlife management purposes, something that was likely beneficial for ivorybills. As Native Americans were exterminated, pushed out of their original homelands, or confined to small reservations, and as European settlers tried to control or eliminate fires, a significant factor contributing to tree mortality was likely reduced, dramatically.

Fulton’s invention of a commercially viable steamboat in 1807 revolutionized commerce, drastically accelerating the clearing of log jams from many watersheds in eastern North America. It’s fair to say that “widespread removal of instream wood for steamboat routes, timber rafts, and flood control was equally significant in decreasing floodplain sedimentation and river complexity, and in causing a fundamental, extensive, and intensive change in forested river corridors throughout the United States.” (Wohl, 2014.) As with changes in fire regimes, this clearing of log jams likely led to a decline in the number of stressed and dying trees along the riparian corridors that seem to have been so important for the ivorybill.

Perhaps equally if not more important in my view is the extirpation of the beaver. It is almost impossible to overstate the role of the beaver in shaping ecosystems throughout North America, a subject that’s addressed in engaging detail in Frances Backhouse’s Once They Were Hats. Beavers help create conditions that are good for woodpeckers by stressing and killing trees, through foraging and by changing hydrology. I’ve never tried to quantify it, but many, perhaps most, medium to large sized sweet gums in our search area show signs of beaver damage, and many others have been killed or severely weakened by beaver-caused flooding.

While beavers are not native to peninsular Florida, the ivorybill’s dwindling range elsewhere roughly tracks their decline; with extirpation starting in the northeast, moving West, and then South. (Southern beaver pelts were less valuable.) By 1900, beavers had disappeared from most of the southeastern US, and in Tanner’s day, a very small population persisted in the Florida Parishes of eastern Louisiana. Reintroductions began in the 1950s, and beavers are now considered a pest animal in Louisiana. It’s worth pointing out that the introduced beaver population in Tierra del Fuego appears to be benefitting the native Magellanic Woodpecker (Soto et al. 2012).

The resurgence of the beaver throughout the southeastern US is almost certainly producing substantially improved habitat conditions in many places. While the old growth forests may be virtually gone, it’s not inconceivable that ivorybill food sources are considerably more abundant now than they were in Tanner’s day, and if the species survived, conditions may actually be more favorable than they were in the 1930s and ’40s. It’s also worth pointing out that the southeastern United States is one of the few places in the world where forest cover has increased substantially in the 21st century.

It should be clear to readers of this series that the Ivory-billed Woodpecker inhabited a larger range and was able to exist in more varied habitats than most publications on the species suggest. This has implications for searchers and for what is deemed to be suitable habitat. For example, the trail cam images from the old Project Coyote search area were obtained near the edge of a bean field, and the putative ivorybill roost holes were in willows (more on that in my next post). Since ivorybills in the western part of their range seem to have lived in willow and cottonwood dominated riparian corridors, fast growing, short-lived willows might have played an important role in the species’ survival in other areas too, although willow-dominated habitat would be dismissed as unsuitable under conventional standards of habitat appropriateness.

It seems to me that even a slightly higher degree of adaptability would increase both the chances of survival and the likelihood that surviving populations might be overlooked due to preconceptions about habitat “suitability” ; this was doubtless one of the factors that led officials to dismiss the landowner in our old search area. Now that beavers are again abundant in the southeast, habitat that might otherwise have been deemed “unsuitable” may now be able to support ivorybills, even if the forest itself is not very old. While I don’t envision a recovery along the lines of what’s happened to the Pileated since my youth (when seeing my first one was a thrill as much for its scarcity as its beauty), I think it’s possible that ivorybill numbers have been increasing gradually and modestly over the past few decades. There was, of course, fairly intensive searching from around 2000-2010 (though it’s mostly over now), but it may be that the more numerous sightings from this period and afterwards are due to more than just the increased effort.

*The remains found in Native American middens were unlikely to have been trade goods; ivorybill parts seem to have been a valuable commodity for ceremonial use west of the Mississippi but not east of it, and in several cases, the remains found were tarsometatarsi, which would be consistent with use as food:

There is strong physical evidence of  ritual value for woodpecker scalps and bills from the upper Midwest and Plains . . .  Remains of the Ivory-billed Woodpecker can be found in sacred bundles, on pipe stems, on amulets, and with burials among the Native Americans of the region. The evidence comes from the western Great Lakes and the Plains; no
evidence of a particular use of Ivory-billed Woodpeckers has yet been un-
covered from the eastern area of the Great Lakes (Ohio, Indiana, and Michigan).

(Leese, 2006.) Leese also points out (in several of his publications) that there’s no evidence that ivorybill parts other than scalps and bills had any trade value.

A number of these midden records were accepted by Tanner in his unpublished 1989 update.


Bits and Pieces Part 5: More on Range and Habitat Variety

I intended this long-delayed installment in the “Bits and Pieces” series to be the year’s final post. I also intended it to the be final installment in the series. While this may end up as the last post for 2017, I’ve decided to cut this short and save some discussion for what I anticipate will REALLY be the final installment.

Follow the links for Parts 1, 2, 3, and 4.

I’ll begin by reiterating that my focus here is not just on records from outside what’s commonly believed to be the historic range but also on records from habitats that depart from the stereotype that has emerged since the 1940s. Those who have studied the ivorybill’s natural history in depth understand that the species was not limited to Singer Tract-like habitats, and Tanner himself made this clear. Nevertheless, there’s a widespread tendency to think about habitat quality with a somewhat romanticized image of the Singer Tract – a vast contiguous area of old growth or virgin forest with huge trees and a high canopy – as the touchstone.

Ivorybill anatomy is specialized and particularly well-adapted to scaling bark, but the specialization pertains to securing food sources not easily retrieved by other woodpeckers (including Pileated) during the breeding season; it is not a specialization tied to particular tree species or habitat types.

Before moving on to a discussion of other records that don’t fit the Singer Tract model, I wanted to address something Cyberthrush said in an October post linking to this series. He wrote:

One of my hopes for the widespread USFWS/Cornell search was that it would at least narrow any possible IBWO persistence down to a very few (perhaps 2-3) localized areas; instead the failed endeavor left open the possibility of 2 dozen or more (sometimes little-birded) areas that scarce IBWOs might conceivably utilize. The lack of a single Ivory-billed Woodpecker appearing on remote, automatic cameras by now at more traditional and well-searched areas remains a pretty devastating obstacle to hope for the species… unless indeed it has found a home in the canopies of less-obvious, lightly human-trafficked woodlands.

I don’t want to hold out too much false(?) hope for this species, but on the other hand I believe most southeast woodland habitat is rarely birded in any regular or significant fashion and the vast majority of individual woodland birds are never systematically recorded — moreover, the ornithological literature is rife with weak, unscientific conclusions/generalizations/assumptions about bird behavior, and perhaps even bird biology. There’s just a lot we don’t know, while pretending we do.

While I don’t share Cyberthrush’s perspective on the lack of remote camera photos (or canopies), he makes very good points about the overall paucity of birding activity in many southeastern forests (I have never encountered other birders in the field) and about the limits of our knowledge.

With regard to his disappointment in the organized search effort, I suspect his hopes were founded in part on similar internalized beliefs; these beliefs were reflected to some extent in the excellent lists of potential habitat compiled by Bob Russell and Bill Pulliam that were so widely referenced a decade or so ago. That’s not to say the listed locations were unworthy of attention (and some of them have yet to receive much); however, there are many other areas that were not included.

In discussing his search efforts in one of these areas, Bill summed it up very well:

Many forest birds have modified their habitat usage in recent decades and centuries. Chimney Swifts are an obvious example; also quite telling is the Vaux’s Swift which has only begun moving out of old growth and into chimneys in the last few decades. But of more direct relevance, consider the following quotes:

When found they are usually in regions of original forest growth, rarely being seen where the woods have been once cut over. […] As this Woodpecker seems not to possess the faculty of adapting itself to the new conditions created by civilization, it is quite possible that it will not long survive the passing of our primeval forests. T. Gilbert Pearson, Birds of America, 1936.

Its presence in a region is more often revealed by the large cavities it excavates in dead stumps and trunks than by actual observation of the bird itself. […] This species is common only in the wilder parts of its range. Frank M. Chapman, Handbook of Birds of Eastern North America, 1939.

Both of these early 20th Century characterizations are of the habitat requirements of the Pileated Woodpecker. In fact, as we all know, over the intervening decades Pileateds managed to adapt to forest fragmentation and second growth quite well, thank you, and are now widespread in habitats well beyond the range of what was described in the 1930s.

There’s also another fundamental, perhaps somewhat tautological factor at work. If in fact Ivorybills were an obligate old-growth bird, then yes, they are now extinct. If they were never able to utilize second growth and fragmented forest, then there is absolutely no reason to be looking for them now anywhere. But even given the historical accounts of their habits they demonstrated a bit more flexibility than this; and given the actual history of Pileateds and various other forest birds since the industrial revolution, it seems brash and unjustified to presume that the habitat utilization of a 21st Century Ivorybill would be the same as that of one in the 19th Century.

We now know that even within the Singer Tract, ivorybills nested successfully at Mack’s Bayou, an area that was predominantly second growth, and I’d suggest that ivorybills showed more than “a bit more flexibility”, when one looks at the historical record.

As Fangsheath at ibwo.net has pointed out both on the forum and in an email, most of the ivorybill localities referenced by Tanner are from within 20 miles of the coast, and “[t]hese coastal forests are quite different from the Singer Tract.” In many of these coastal areas, tree size would have been smaller, the understory would have been thicker, and the canopy would have been lower due to hurricanes and other factors. In addition, the coastal records may have implications for survival in fragmented habitat types.

There are a number of records from Florida and South Carolina involving offshore islands. While most if not all of these offshore islands would have been covered in old growth forest at the time of collection, reaching them would have required crossing expanses of open water or marsh.

In South Carolina, there were multiple reports from barrier islands into the 1880s. A specimen collected in 1879 or 1880 is now lost. Hoxie, writing in 1918, reported that ivorybills were generally “unpersecuated or harmed by man” and that they had opportunistically fed on the barrier islands, following hurricanes, but disappeared when the food supply was exhausted.

My knowledge about Florida and conditions there is limited, but it seems clear that ivorybills lived and bred in a variety of habitats. Florida is also the largest single source of specimens and probably had the largest ivorybill population in the country. What may also be relevant is their apparent use of of mangrove forests, including potentially some 1-2 miles away from the mainland, especially in the Everglades region. As with barrier islands, use of this habitat may have involved crossing some open water between mainland forests (e.g., Big Cypress, associated forested sloughs, and open pine woods, leading to the Gulf of Mexico) and mangrove forests, both along the coastline and in the area referred to as the Ten Thousand Islands, extending south to where Tanner relayed reports during the 1930s from Shark and Lostman’s Rivers within what is now Everglades National Park.

To end this tour of ‘unexpected’ habitats and ‘extralimital’ records, let’s jump north and west by a thousand miles or so and consider records from Arkansas/Missouri and Virginia.

The Arkansas/Missouri records are from George Featherstonhaugh who explored the area in the 1830s and published his account in 1844 as Excursion Through the Slave States from Washington on the Potomac to the Frontier of Mexico; with Sketches of Popular Manners and Geological Notices. Featherstonhaugh reported seeing ivorybills in two different locations – one from a bottomland area above the confluence of the Ouachita and Caddo Rivers, in the vicinity of present day Arkadelphia, AR. This passage is from Volume 2.

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The second location appears in Volume 1 and is more interesting for the purposes of this discussion, since it involves fire damaged upland forest, likely oak-dominated, with hickory and perhaps some shortleaf pine. It’s not clear whether the site is in present day Arkansas or present day Missouri. Either way, it appears to be on the edge of the Ozark Plateau where it meets the Mississippi Alluvial Plain. As an aside, Featherstonhaugh seems to have had an eye for detail and a dry sense of humor:

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Whether the birds were resident in this area or were merely feeding opportunistically in the fire damaged table-land, the habitat involved bears no resemblance to the Spanish Moss festooned, swamp forest stereotype.

Thomas Jefferson included the ivorybill on his list of Virginia birds found in Notes on the State of Virginia (1785). While some authors have suggested that Jefferson was merely following Catesby, it has also been argued that Jefferson’s list was “a product of his personal observations”. If this is true, Jefferson’s observation would not have been from the Great Dismal Swamp (where Pearson thought ivorybills might be present in the early 20th-century), since Jefferson never went south of Norfolk.

Thomas Nuttall, writing in the 1830s, described the ivorybill as being “seldom seen to the north of Virginia and rarely in that state.” In The History of Ornithology in Virginia (2003), Johnston dismisses Nuttall’s assertion but also points to a much earlier and unambiguous record from an upland site, one that seems to have been otherwise overlooked.

The record is from a Native American midden dating to the early Woodland period, ca. 300 CE (AD). The site, Daugherty’s Cave, was used for millennia. It’s in the western part of the state, far from the coastal plain, at an elevation of approximately 2000′. The context suggests that the remains were not trade goods, and Johnston deems it to be “the only known record of this bird from Virginia”.

I’m struck by the fact that if the ivorybill had gone extinct before 1700, and we only had the scant archaeological record to go on, we’d imagine it to be a bird associated with upland forests. On a more serious note and perhaps one more relevant to the discussion that will follow in the next post, I wonder whether the appearance of ivorybill remains in Appalachian middens around 1800 years ago is related to the spread of maize agriculture and tree kills associated with this new farming technology.

So what inferences can be drawn from all this information and what are the implications? I have some thoughts, not all of them had occurred to me before I began  this exploration, and I hope they’ll inspire readers to reflect and come up with their own new insights.

The first and perhaps most mundane observation is that the range maps with which we’re all so familiar, like the one below from the IUCN, reflect the ivorybill’s status after what was likely a long period of decline, especially east of the Mississippi. Unfortunately, these maps reinforce ideas about habitat requirements and tree species associations that are, at best, oversimplifications.

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For contrast, I’ve updated the map I created showing most of the records discussed in this series.

This is not to suggest that reports from outside this “historic” range should be taken seriously today. The map is a fairly accurate reflection of the reality post-Civil War. The more important questions are why the range started to shrink, probably during the 18th-century, and what this more complex analysis of potential habitat types might imply for the species’ survival. That will be the subject of the next and final installment.


Bits and Pieces Part 4: Rethinking Range and “Suitable Habitat”

Part 1.

Part 2.

Part 3.

Bottom line upfront: In pre-contact and early colonial times and into the 19th century, Ivory-billed Woodpeckers inhabited a more varied and expansive range than most people realize. The range probably reached from the southern tip of Florida to central Ohio, with the 40th parallel as the approximate northern limit, westward to St. Louis and perhaps along the Missouri River. As discussed in the previous post, the western limit of the range appears to have been somewhere around the 96 or 97th Meridian, in the southwest, and probably somewhat farther east at the northwestern edge, if unproven historic reports from the Kansas City area are valid. Outside of coastal areas, distribution appears to have followed riparian corridors to its outer limits, and there are no records from elevations of over ~1000′.

A couple of maps may be useful for additional information about forest, bioregion, and habitat types and may help with visualization along with my map of records from unexpected habitats.

This is a new avenue of exploration for me, and I’m not personally familiar with many of the areas involved. I need to do additional research on areas within Tanner’s range map, along the coasts and in Florida, to be sure my characterizations are accurate. I’m leaving some of these locations on the master map for now (but removing them from the graphic below which includes extralimital and edge of range records). The master map is thus subject to change, so view it with the caveat that the notations may be incomplete or inaccurate. This post will address locations that are outside the confines of Tanner’s 1942 range map, although he accepted some of these records in 1989.

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As in the previous post, my analysis relies on records accompanied by reported physical evidence (even if that evidence has been lost) and to Native American sites where remains found are deemed unlikely to have been trade items. I relied on the US Fish and Wildlife Service’s Recovery Plan, Appendix E, Tanner, Jackson, and a few additional sources.

Before undertaking a whirlwind tour of the locations involved, I thought I should return to the mythology discussed in the previous post. I chose my words poorly in describing that mythology: “To a large extent these beliefs treat the Singer Tract as a model – a vast tract of “virgin” bottomland forest dominated by oaks and sweetgums, with abundant, moss-draped cypress for atmosphere (although ivorybills seem to have avoided cypress in the Tract).”

In fairness to Tanner, he didn’t characterize cypress as being abundant in the Tract. (It was not.) And his overall view was that cypress-tupelo swamps were not good ivorybill habitat. Audubon, with his romantic, indeed gothic, language is the father of the cypress myth.

I wish, kind reader, it were in my power to present to your mind’s eye the favourite resort of the Ivory-billed Woodpecker. Would that I could describe the extent of those deep morasses, overshadowed by millions of gigantic dark cypresses, spreading their sturdy moss-covered branches, as if to admonish intruding man to pause and reflect on the many difficulties which he must encounter, should he persist in venturing farther into their almost inaccessible recesses, extending for miles before him, where he should be interrupted by huge projecting branches, here and there the massy trunk of a fallen and decaying tree, and thousands of creeping and twining plants of numberless species! Would that I could represent to you the dangerous nature of the ground, its oozing, spongy, and miry disposition, although covered with a beautiful but treacherous carpeting, composed of the richest mosses, flags, and water-lilies, no sooner receiving the pressure of the foot than it yields and endangers the very life of the adventurer, whilst here and there, as he approaches an opening, that proves merely a lake of black muddy water, his ear is assailed by the dismal croaking of innumerable frogs, the hissing of serpents, or the bellowing of alligators! Would that I could give you an idea of the sultry pestiferous atmosphere that nearly suffocates the intruder during the meridian heat of our dogdays, in those gloomy and horrible swamps! But the attempt to picture these scenes would be vain. Nothing short of ocular demonstration can impress any adequate idea of them. 

Hasbrouck (1891) perpetuated the emphasis on cypress and very low-lying locations:

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Hasbrouck’s explanation of the Missouri extralimital records is odd. The locations given are well outside bald cypress range.

That aside, the myth discussed in the previous post is a composite. The emphasis on cypress originates with Audubon and Hasbrouck, and the emphasis on large tracts, old growth, oaks, sweetgums, and tree size is largely drawn from Tanner.

Here are the extralimital records:

Reedy River, South Carolina: Nest with eggs reportedly collected in 1896 and later lost. The location is in the Piedmont, south of Greenville, at an elevation of approximately 900′. The Reedy flows into the Salad, which flows into the Congaree. This report is listed in the Recovery Plan because it was accepted by Sprunt as “definitive” but is considered highly questionable.

Etowah Mounds, Georgia: Pre-contact site, elevation approximately 700′. Presumably not trade goods “but requires further discussion” per the Recovery Plan. The Etowah River is at the northern end of the Alabama River watershed.

Between Martinsburg, West Virginia and Winchester, Virginia: Specimen reportedly collected by Wilson ca. 1810. Elevation at Winchester is 725′ and at Martinsburg is 453′. This would appear to be in the Potomac watershed.

Edited to add: This report is probably based on an incorrect inference. (Leese and Michaels, 2020)

Moundsville, West Virginia: Two lower mandibles found in a pre-contact (early Common Era, 0-200) midden. Potentially trade goods. Elevation 696′. The location is on the Ohio River.

Philo, Ohio: Near the Muskingum River. Tarsometatarsus found in pre-contact midden, dates from ca. 1100-1500. Elevation 735′.

Sciotto County, Ohio: Same as above. Elevation of the site is 1050′, but the nearby Sciotto River is lower. The site is about 10 miles from the Ohio, and the elevation at the confluence is 533′.

Ross County, Ohio: Same as above. Also on the Sciotto River but farther upstream. Elevation 863′

Near Troy, Ohio: Near the Miami River, March 1804 sight record by Gerard Hopkins, a Quaker envoy to the Miami and Pottwatomi. The report includes a description, “. . . resembling the red headed woodcock of Maryland, except that its head is black and its bill ivory. ” (Leese 2001). Omitted from the map because it doesn’t involve a specimen, but included here because it adds weight to the archaeological records.

Franklin County, Indiana: Report of a specimen, 1869, now lost. Elevation at least 490′. Probably along the Whitewater River, an Ohio tributary. There are a number of early reports from Indiana, but no other reported specimens and no archaeological records. In light of Audubon’s collection at Henderson, KY (just across the Ohio River) as well as the Ohio records, it seems likely that ivorybills were present in parts of Indiana into the 19th century.

Henderson, Kentucky: Female specimen collected by Audubon in July 1810 and used as a model for his first painting of the species. Elevation 400′. This record does not appear in the Recovery Plan or Jackson, and it seems to have been overlooked by researchers. Audubon’s own notation describes the location as “Red Banks”, on the Ohio River at the northernmost limit of the cypress-tupelo association, well upstream from the confluence with the Mississippi. Article by R. Haven Wiley in Kentucky Warbler, May 1970.

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Stanford, Kentucky: Pair reported, with one specimen collected by a Colonel Fleming, 1790. Record accepted by Tanner in 1989. Elevation 942′. The Dix River, which flows into the Kentucky and thence the Ohio, is nearby.

Cahokia Mounds, Illinois: East of the confluence of the Mississippi and the Missouri, 1500s or earlier, tarsometatarsus. Elevation 490′.

Forest Park, Missouri or Vicinity: West of the confluence of  the Mississippi and Missouri. Specimen collected 1896 and in the collection of the Colorado Museum of Natural History. Elevation approximately 500′.

I find it interesting that Ohio is the state with the most pre-contact records involving likely food items – 3 out of a total of 4-6.

With regard to Missouri and the Missouri River watershed, Hasbrouck accepted reports from Fayette and Kansas City, and given the overall picture, this does not seem implausible. In addition, there were persistent reports from the vicinity of Lake of the Ozarks, in the Missouri River watershed, until the end of the 1940s; Tanner received information about Missouri reports from local Audubon society officers but apparently disregarded it. There’s no way to assess the validity of these old, anecdotal claims and no evidence to support them, but given this perspective on the historic range, they may be somewhat less far-fetched than it seems at first glance.

I’m heading for Louisiana soon. More after I return – a trip report and probably two additional installments.


Bits and Pieces Part 3: Internalized Beliefs, How They Got That Way, and What the Record Really Shows

Part 1 is here. Part 2 is here. It looks like this series will end up being a five-parter. Part 4 should follow later this week and Part 5 sometime thereafter.

Most of us with an interest in the ivorybill have internalized a set of beliefs about what constitutes “suitable” habitat. To a large extent these beliefs treat the Singer Tract as a model – a vast tract of “virgin” bottomland forest dominated by oaks and sweetgums, with abundant, moss-draped cypress for atmosphere (although ivorybills seem to have avoided cypress in the Tract). The habitat description in Stephen A. Shunk’s excellent Peterson Reference Guide to Woodpeckers of North America clearly expresses some of these beliefs, which have influenced the overwhelming majority of modern search efforts and which are embedded in the minds of most searchers (myself included) to the point of being a default:

Virgin bottomland forest almost always below 100 ft. (30 m) elevation. May also have occurred in uplands but by 1900 restricted to areas downstream of pine-bald cypress interface. Requires large tracts of contiguous forest with very large-diameter trees and adequate dead and dying trees to provide forage and nest sites.

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The Guide, which draws on an 1891 article by Hasbrouck for the 100 foot elevation, goes on to list three different habitat types described by Tanner – sweet gum-oak dominated forests in the southeast (with species of oak varying depending on location) outside of Florida; river swamps in Florida dominated by cypress, black gum, and green ash; and creek swamps in Florida characterized by cypress, red maple, laurel oak, black gum and cabbage palmetto, with feeding in adjacent pine woods.

This is not to criticize the Guide or its author – I recommend the book highly and the overall treatment of the ivorybill is thorough and evenhanded. The quote is intended to point out the pervasiveness of these ideas about habitat requirements, ideas that Tanner reinforced, especially in later years. They’re so pervasive in part because the myth of the “virgin forest” has shaped ivorybill lore since well before Hasbrouck and has influenced almost all habitat assessments since Tanner.

The virgin forest myth is a topic for another day; the central point is that ivorybills have been found in more diverse habitat types than most have believed. It’s worth bearing in mind that Tanner himself asserted that ” . . . at present the only suitable habitat for ivorybills is in tracts or areas of virgin timber”, a narrow, almost lawyerly, and largely conjectural conclusion – one not entirely supported by fact. Ivorybills bred in at least one Singer Tract area (Mack’s Bayou) that was predominantly regrowth, and as has been discussed in previous posts, Tanner became more dogmatic and blinkered about habitat requirements in later years, dismissing the John Dennis Texas recording because a Pine Warbler was captured on the tape.

As should become clear, Ivory-billed Woodpeckers were found in a variety of different habitats and did not always require extensive tracts of contiguous forest. Large diameter trees, their importance, and what Tanner meant by “large” are discussed in another post, but even if one accepts that large trees were preferred in the Singer Tract, much of the feeding sign Allen and Kellogg documented in Florida was on small, fire-killed pines.

My plan for this post was to focus on Ivory-billed Woodpecker records from outside the historic range as delineated by Tanner in his oft-reprinted 1942 map and adaptations thereof.

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US Fish and Wildlife Service range map based on Tanner, including locations of selected post- Singer Tract reports

The purpose behind this original plan was in part to show that the historic range of the ivorybill was considerably more extensive than is commonly believed, but more importantly to show that ivorybills inhabited more varied habitats than is commonly believed. As time went on, my focus has shifted even more toward the question of habitat diversity, though the fact remains that the historic range was considerably more extensive than the Tanner map, or the one drawn by Hasbrouck in the 1890s, might lead one to expect.

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Hasbrouck’s Ivory-billed Woodpecker Range Map (1890)

In recent Facebook comments, several ornithologists have suggested that without physical evidence, no record should be accepted. As I see it, this standard is, to some extent, a kind of ahistorical overkill, since it has never been applied in the past. Post-1939 Singer Tract observations don’t meet it, so the last record date is pushed back by several years, which can impact statistical analyses. At the same time, the parsimonious approach is not entirely meritless, since it eliminates false positives. The problem is that there’s no purely objective standard for evaluation of historic (and pre-contact) records, even when it comes to specimens. In many cases, location information for specimens is non-existent or ambiguous; for example, one specimen in Cornell’s collection (1896) is listed as coming from the “Florida Keys”; “Key” in this context more likely refers to an island of forest surrounded by the Everglades than to the islands offshore.

Thus, in this post and the next, I’ll be looking at many reports from within the recognized historic range, as well as some from beyond those boundaries. I will be focusing on reports accompanied by physical evidence or published accounts stating that physical evidence was obtained but will include or mention a few additional ones that seem particularly credible based on the source or amount of detail.

The more surprising of these reports are unsupported by physical evidence. These come from the Eastern Shore of Maryland, Swedesboro, New Jersey, and Pennsylvania. Most date to the 18th-century, a time when ivorybills were reported to have fed on trees girdled for clearing. The most interesting of these come from Peter Kalm, a Swedish naturalist and student of Linnaeus. They have been discussed in several articles by Benjamin Leese, who has also written about early records from Ohio, Indiana, and Kentucky (for which the case is stronger). Most of these papers do not seem to be available online.

Just under 200 of the 418 specimens (including Cuban ivorybills) listed by Hahn provide no location information or merely identify the state, or country in the case of Cuba, where the collection took place. There are multiple cases in which specimens were reportedly collected but have not been found, and in several cases, there’s no way to correlate the claim of collection with an actual specimen. In one instance, not catalogued by Hahn, a pair of ivorybill specimens was mislabeled as Pileated Woodpecker until the error was corrected in the 1960s.

When it comes to pre-Columbian sites, there’s no way to be certain whether material collected from graves and middens involves trade goods or locally killed animals, although tarsometatarsi are likely local, especially east of the Mississippi, where there’s little evidence to suggest that woodpeckers had ceremonial value. Leese addresses this subject in a paper on Native American uses of ivorybill parts. I have included records involving tarsometatarsi and one from a West Virginia midden that involves parts of two lower mandibles.

I’ve created a google map showing the locations of the records from habitat types that don’t fit the ‘large tracts of contiguous bottomland forest’ paradigm. I’ve provided some details for each location. The map draws on Appendix E or the US Fish and Wildlife Service’s Recovery Plan, Tanner, and Jackson. I’ll discuss the records from coastal areas, south Florida, the upper Mississippi and locations east of the river in the next post. I’ll conclude this one with a look at the records from the western edge of the range, since they relate to the Nebraska report and why I thought it might be credible; the Nebraska location is actually somewhat east of the records from the southern plains.

One record that I find compelling does not include a specimen; it’s from the 1820 Long Expedition, the first scientific exploration of the American West. Screen Shot 2017-10-08 at 8.08.14 AM

The ivorybill’s call is described, and Pileated Woodpecker is distinguished and described as common in the area. These facts lend credibility to the report, as does the fact that Thomas Say was the expedition’s naturalist. While Say is best known as an entomologist, the expedition produced the first descriptions of a number of bird species, and an entire genus of flycatchers was named in his honor.

The location of this record is approximately south of Tulsa on the Canadian River, near the 96th Meridian. This is farther west than the location of the erroneous southeastern Nebraska report and well into the eastern Great Plains. It is also well beyond the range of the bald cypress. The relatively narrow floodplain would have been dominated by cottonwoods and willows, as it is to this day. This image, from ca. 1920s shows “Standing Rock” a geological feature now flooded that was discovered by the expedition a day after the ivorybill encounter. It should add a visceral sense of the area’s appearance to supplement the description above.

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Even if one opts to reject this record for lack of physical evidence, there are several others from approximately the same longitude that do involve specimens, and some are from the 20th century.

The Recovery Plan suggests that there are two records from west of Tulsa, a specimen was “probably” collected by Woodhouse along the Cimarron River, Pawnee County in 1849. Per Jackson, the specimen was sent to the Philadelphia Academy of Natural Sciences, which has four specimens without location information in its collection. The second is from House Creek in Pawnee County, also Woodhouse 1849, and also reportedly sent to the Philadelphia Academy but not found there.

There are several Plains records from Texas. A specimen currently in the Dallas Museum was collected on Bois d’Arc Island, just southeast of Dallas, elevation 400′, in 1900. There were multiple reports from the area through 1910, and an additional bird may have been collected in 1918. A bird was reportedly “caught in a trap” in nearby Kaufman County in 1927 and examined by an R.E. Huck but not preserved. An additional Texas record, from farther south but west of the 96th Meridian, comes from New Braunfels County, south of Austin and east of San Antonio. There were multiple reports ca. 1900, with a collection reported but no specimen preserved.

Although only one record from the eastern Plains can be attached with certainty to a currently existing museum specimen, there’s proof that Ivory-billed Woodpeckers were found in this region as recently as 1900 and considerable circumstantial evidence for their presence along riparian corridors on the plains of Texas, and possibly Oklahoma,  into the 20th-century. The habitat involved is markedly different from what so many have believed ivorybills require. I’m not suggesting that ivorybills persist at the western edges of their historic range, but as will be discussed in the final installment of this series, I think their ability to exploit these relatively narrow, willow and cottonwood dominated floodplains can help explain how the species could have persisted into the 21st century.

Stay tuned for Part 4.


Bits ‘n’ Pieces Part 2: A 19th Century Report from . . . Nebraska? Updated – Turns Out to Be Pileated.

Update and correction: Since writing this post, I have sought additional information, and it appears that the record was due to a miscommunication (not an erroneous report or false claim). It turns out it was retracted as pertaining to Pileated Woodpecker a few years later (T. Labedz, pers. comm.). Pileated Woodpeckers were extirpated in Nebraska ca. 1900 and only resumed breeding there in the late 20th century. Rather than delete this post, I will leave it up. I stand by the broader point about internalized beliefs and the variety of habitat types in which ivorybills were found in the past. More on that to come.

Part 1 is here.

What I envisioned as a single post has evolved into a series, as sometimes happens when I start digging into a topic. I started looking at reports from the edges of or outside the range described and mapped by Tanner in the monograph. (At the time, he was unaware of a number of these reports, some of which he accepted in 1989.)

I’ll be discussing those records and some others in the next post. For now, I’ll be focusing on one that seems to have been missed by other researchers. At first glance, it may seem improbable, since it goes against internalized beliefs about “suitable” habitat and extensive tracts of southern bottomland hardwood swamps as a requirement. While I’ve been a frequent critic of these beliefs, they’re part of the ivorybill legend, and they still affect me.

In the end, I think there is some basis for treating this report, which appeared in the 1896 Proceedings of the Nebraska Horticultural Society, as credible. It comes from Nemaha County, in the southeastern corner of the state, approximately 100 miles NNW of Kansas City.

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It’s worth pointing out that Audubon described the ivorybill’s range as extending to the “very declivities (slopes) of the Rockies.” This was undoubtedly mistaken, but Hasbrouck (1891)treated Kansas City as the northwesternmost edge of the range. Several of the records accepted by Tanner in the monograph come from farther west in Oklahoma and Texas, in the Red and Arkansas River watersheds. I’ll have more on the range descriptions from these three authors in the next post, but the evidence suggests that the post-contact range followed riparian corridors and extended into the eastern Great Plains. Thus, a 19th century record from southeastern Nebraska is not as far-fetched as it might seem.

After I found this record, I did some research on G.A. Coleman, who was cited 66 times in the 1896 compilation of state records, including for Yellow-bellied Sapsucker and Downy, Hairy, Red-headed Woodpeckers. He was not cited for Pileated, which was described as rare or a winter visitor along the Missouri.

The first reference I could find for Coleman was a description of American Coot behavior in the January 1, 1887 edition of Ornithologist and Oölogist. It mentions that Coleman had attended The Normal School in Peru, so he had some college education. Coleman remained active in Nebraska until around 1901 and appears to have  been respected in ornithological and mammalogical circles. He is cited and quoted in several journals, and in 1892, he stood in for the chairman of the ornithology committee and delivered a brief paper to the State Horticultural Society. In the presentation, Coleman mentioned the Agriculture Department’s Division of Economic Ornithology and Mammalogy, a government body that would soon become his employer.

I was able to find some additional information about Coleman and the Division of Economic Ornithology and Mammalogy in a U.S. Geological Survey publication:

. . . [O]n the 3d of March, 1885, Congress appropriated $5,000 for the promotion of “economic ornithology, or the study of the interrelation of birds and agriculture, an investigation of the food, habits, and migrations of birds in relation to both insects and plants.” The money became available on the first of July following. Upon the recommendation of the American Ornithologists’ Union, Dr. C. Hart Merriam, physician and lifelong student of natural history, was appointed head of the new project. He selected as his assistant Dr. A. K. Fisher, also well trained in field zoology and botany, and a graduate in medicine, and these two men, with a secretary, who in 1886 became Mrs. Merriam and was succeeded by Mrs. A. B. Morrison, constituted the entire force of the new organization. It was first established as a branch of the Division of Entomology. The year following the appropriation was doubled and the unit became an independent “Division of Economic Ornithology and Mammalogy.” In 1896 the name was changed to “Division of Biological Survey.” On March 3, 1905, just twenty years after the date of the first appropriation, the name was changed to the Bureau of Biological Survey.

Gradually, through the years, the little band that started the Survey–the Division of Ornithology and Mammalogy–was enlarged by the enlistment of other naturalists, mainly young men raised in many States from New England to California, who from boyhood had studied the birds and mammals and other wild inhabitants of the woods and fields about their rural homes, and including also a number of older men with extensive field and laboratory experience in various phases of natural-history study. During this period both Merriam and Fisher, for a part of nearly every year, carried on field work, mainly in the Western States or in Alaska, and published widely on their findings.

. . .

April 1892 witnessed the addition to the Survey’s field force of J. Alden Loring, of New York. Loring was an enthusiastic collector, and during the next few years worked in most of the Western States and the southern part of the central Provinces of Canada. At this period the standard salary for a field man was $100 a month, from which he had to pay all or nearly all his field expenses. For example, Loring thus financed two expeditions into the Rocky Mountains west of Edmonton, Alberta, the scene of the early labors of David Douglas and Thomas Drummond, by being allowed to spend the winter in Washington, and saving up for the summer’s work. Loring left the service in 1897, but was reemployed for special duties on several occasions, notably in 1920, when he spent the summer on the great waterfowl breeding grounds in central Canada.

In April of the same year Russell J. Thompson and George A. Coleman received appointments to do field work, and after a few weeks training (along with Loring) under Vernon Bailey were assigned separate itineraries. Thompson worked in Georgia, Mississippi,ouisiana, and Tennessee during that summer and fall. Coleman began work in Mississippi, and later collected in Louisiana, Kentucky and Nebraska. Neither remained in the service later than 1893.

Coleman’s field book (along with Thompson’s) is housed at the Smithsonian, but it has not been digitized. Thompson’s has, and it reveals that the two spent a brief period together, collecting in Mississippi and Louisiana.
Given the awareness of the ivorybill’s declining numbers, given the interest in the species that existed in the 1890s, and given the fact that Coleman was collecting in states where ivorybills were extant, it seems likely that Coleman would have been schooled in the differences between Ivory-billed and Pileated Woodpeckers in the course of his training, if he wasn’t already aware of them. I think this lends some additional credibility to his report and places it on or near a par with quite a few other records that have been accepted by Tanner and others. Of course, it lacks a detailed description, and without a specimen, it will always be open to question.
A couple of final thoughts on the habitat: most of the county was unforested in 1856, as would be expected on the eastern Plains. It has been described as “hilly”, encompassing densely wooded hills and bluffs, broken by numerous valleys and ravines. The dominant species included willows, cottonwoods, lindens, box elders, and sycamores in the lower areas and various oaks, hickories, walnuts, elms, ashes, and cherries in the uplands. Forest cover only decreased by 11% between 1856 and 1955, and in 1856, it comprised less than 5.5% of the county’s total area, under 10,000 hectares/38.6 square miles, mostly along narrow riparian corridors or in isolated patches surrounded by prairie.
Similar characteristics probably existed in other locations at the western edges of the ivorybill’s historic range. If this and other reports indeed pertain to ivorybills, they were using habitat (even as vagrants) that differs markedly from the southern swamp forests that figure so heavily in popular lore.
To be continued.

Bits ‘n’ Pieces Part 1 – Louisiana Conservationist

I’ve been reviewing copies of Louisiana Conservationist (formerly Louisiana Conservation Review), the official publication of the Louisiana Department of Wildlife and Fisheries (formerly the Department of Conservation). Copies of the magazine, which is in the public domain, can be found in the Louisiana Digital Library. In the course of my research, I found one real gem and a couple of interesting pieces of less significance.

The gem is the initial report on the 1932 Singer Tract rediscovery and T. Gilbert Pearson’s visit to the area. Pearson was the first professional ornithologist to observe the Singer Tract birds. I’ve written previously about Pearson’s visit and have referenced newspaper accounts of his observations. At the time, I was focused on feeding sign and the statement about feeding on rotting stumps. As a result, I overlooked the important fact that Pearson had been searching for ivorybills to no avail since 1891; this highlights the difficulty in finding ivorybills, even during the era of relentless collecting.

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The Ivory-Billed Woodpecker: Rare Bird Considered Extinct – Found in Louisiana, Margaret A. Coogan, July 1932, Louisiana Conservation Review

The newspaper articles were somewhat less detailed than Coogan’s account, which includes some interesting tidbits. It seems likely that Pearson himself provided the information to Coogan, either directly or via Armand Daspit. There’s an inaccuracy; the mention of carpenter ants as prey is not supported by the literature.* The only record of nesting in pines is in Thompson (1885), a record that Tanner deemed “questionable”.

Edited to add: Hasbrouck (1891) included a second-hand claim of a nest in pine from northwest Alabama. Tanner accepted the report but possibly not the claim of a nest, as the latter is not mentioned in the monograph.

Somewhat more interesting is the observation, “Occasionally it feeds on the ground like a Flicker”.  In 1937, Allen and Kellogg would publish a paper describing their 1924 observation of a female ivorybill foraging on the ground and “hopping like a Flicker”. It’s possible that Pearson was aware of this observation, and the reference to scaling the bark of dead pines suggests this is so. (There were no pines in the Singer Tract.) At the same time it’s also possible that Pearson observed the Singer Tract birds foraging on the ground or described foraging behavior based on general knowledge of how ivorybills in Florida, where he grew up, typically fed.

The other interesting tidbits from Louisiana Conservationist pertain to possible ivorybill sightings in the 1950s. Both items (letters from readers and responses from state officials) are certainly questionable, but they also point to the way Pileated Woodpecker became the default, even when the description was inconsistent with PIWO.

The first is interesting for its location. Urania, Louisiana is southwest of the Singer Tract and is relatively close to the Project Coyote search areas. It was founded by Harry Hardtner in the 1890s and is considered the birthplace of conservation and reforestation in Louisiana. The image that prompted the letter is included for reference.

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The second letter is peculiar, but the description is considerably more suggestive of ivorybill than Pileated – like a Red-headed Woodpecker but the size of a chicken.

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There’s one additional tidbit that doesn’t pertain to Louisiana. In the past, I’ve wondered about record committee submissions and how many there may have been over the years. A divided Arkansas committee accepted the Big Woods report (a fact that’s often glossed over in the literature), while the Florida committee rejected the Auburn reports. Other than these submissions, I was aware of one from Texas, from out of range and in unlikely habitat. I recently ran across another, from Florida, also rejected but interesting nonetheless. Here it is, for what it’s worth:

Ivory-billed woodpecker, Campephilus principalis.
FOSRC 2011-852. This bird was described from an observation in suburban St. Augustine, St. Johns Co., on 13 April 2011. Although the observation included key characters of the Ivory-billed Woodpecker, such as a white bill and white pattern on the back while perched, the observation was at a distance of 30 m and made without binoculars. It is the Committee’s opinion that the only acceptable submissions of this species would be those with verifiable evidence (e.g, identifiable photographs or video). The recent controversy over video recordings, audio recordings, and sightings in Arkansas (Sibley et al. 2006) and Florida (FOSRC #06-610, Kratter 2008) calls into question whether the species may have persisted into the twenty-first century.

More soon.

*Ants are described as a prey species in Bendire (1895), but this is based on a misreading of Thompson (1885). Allen and Kellogg (1937) mention an observation involving suspected feeding on ants but found no ants or termites when they examined the substrate. The closest thing to evidence for ants as prey involves a Cuban Ivory-billed Woodpecker with a hugely overgrown bill that was observed feeding on arboreal termites – a species not native to the continental United States. It was observed and collected by Gundlach in 1843 and was also being fed grubs by its companions. Jackson speculates that this might have been a young adult bird, but given the extent of the hypertrophy, this strikes me as being somewhat unlikely. I’ll opt for the altruistic possibility that Jackson also posits. (Jackson 2004).


Go Read Bill Pulliam’s Blog While You Can

I had been planning to do a post with various ivorybill related tidbits in anticipation of the search season, which begins next month. That will be coming in a week or so, but I want to say a little more about Bill Pulliam first (beyond his Luneau video analyses, which I think should be dispositive). This decision was inspired in part by one of our advisors who pointed similarities between what Bill observed in Tennessee and what we’re seeing in Louisiana. While the physical characteristics of our old search area seem to have more in common with Moss Island, Tennessee than where we’re currently focused, Bill’s perspectives are relevant to both.

Edited to add: Moss Island is a small wildlife management area encompassing 3400 acres. I’m not sure what percentage is mature bottomland hardwood forest, but there are a variety of other habitat types. Compared to our search areas it is relatively isolated and distant from other large tracts of forest.

As an aside, Cyberthrush also has a post honoring Bill with a link to an eBird tribute.

With comments included, Bill’s series of posts on Moss Island runs to nearly 54,000 words. There’s no telling how long this series will remain readily accessible online, and indeed some of the images and sound files are no longer available. The entire series is worth reading and saving if you’re seriously interested in the ivorybill. It starts here.

On re-reading the posts for the first time in eight years, I’m struck by how much Bill influenced me without my recognizing it and/or how much the evolution of my understanding between  2009 and today is congruent with the ideas he expressed just as I was getting more deeply involved in searching.

Like Bill, I suspect that the near extirpation and revival of the beaver may be central to the ivorybill’s decline and survival (more about this in my next post). Like Bill, I think that Tanner’s model failed to account for environmental changes that had taken place in the preceding centuries. Like Bill, I think that if the ivorybill survived, it had to have adapted in ways that are inconsistent with Tanner’s a priori assumption that the species is old-growth dependent.

Bill was tough-minded and opinionated. There were times when I thought he considered me a somewhat annoying amateur. While we hadn’t communicated about it in recent years, he took a dim view of my efforts to make sense of feeding sign in the early days. Most of our correspondence took place in the 2000s, while he was still actively blogging about the ivorybill. After that, I sought his input sparingly.

My last exchange of emails with him pertained to the March recordings. Without quoting him directly, I think it’s fair to say he thought the calls were likely or more than likely Ivory-billed Woodpecker. He also thought it unlikely that birds were resident in our search area, based on the pattern of potential encounters, the paucity of strong sightings, and lack of conclusive evidence. I’m not sure I agree; I wish there had been a chance to explore this topic in more depth and that he’d been able to see our search area for himself. Nonetheless, his perspective has led me to consider that other nearby forested areas deserve more attention than we’ve given them to date.

I’ll conclude with three paragraphs from his final post in the Moss Island series. It’s as true today as it was in November 2009 (though I suspect nesting may take place in fragmented second growth, as in our old search area). I hope it inspires you to read the rest. More from me soon.

How does this relate to Moss Island? By Cornell standards, our habitat is unsuitable. Hence, our encounters are largely dismissed out of hand. By doing so, the Cornell approach has painted themselves into a rather nasty corner. The logic is simple. To all appearances, we have Campephilus-like double knocks that are at least as good as what has been heard in the “core habitat” such as Big Woods and Congaree. If one claims that in “core habitat” these represent evidence for the possible presence of Ivorybills, but in “marginal” or “unsuitable” habitat they provide no evidence for the possible presence of Ivorybills, one has committed a logical no-no of the first magnitude. If the same sounds come from places where you have concluded that Ivorybills are not going to be, then you should conclude that these sounds have no relevance to Ivorybills anywhere. Conversely, if you feel these sounds are evidence of the possible presence of Ivorybills in South Carolina or Arkansas, then you must also accept that they would be evidence of the same in Tennessee, Illinois, Mississippi, Florida, Louisiana, and Texas. You can’t have it both ways.

Anyone who seriously considers that Ivorybills might still persist, and that double knocks and other soft evidence have a relevance to indicating their possible presence, should accept that the evidence in total suggests their habitat requirements might be broader than has been assumed by Cornell et al. I’m not suggesting they will nest in fragmented second growth, or even use it as a full-time habitat; but there are ample indications that if these sort of encounters mean anything anywhere then the birds indeed are using fragmented “marginal” habitats for at least parts of their life history. These habitats are hugely more extensive than the “core” habitats, hence this possibility raises all sorts of further hypothetical possibilities for the natural history, survival, and conservation of the species, all of them positive. In the alternative philosophy to Cornell’s, you search where you have learned of rumors, whispers, or credible declarations that something of interest might have been seen or heard there. This of course requires a lot of judgement, and eventually everyone will draw the line somewhere; I’d not put much stock in reports from western Kansas, for example — although good double knocks in Nebraska or Vermont would settle a lot about what they might mean in Arkansas! But until and unless we actually find some reproducible birds and determine what their 21st Century habitat use patterns really are, minds should be kept open.

You will not get anyone involved in the Tennessee project to state that we have established the presence of an Ivory-billed Woodpecker anywhere in Tennessee as a statistical or scientific certainty. None of us has put an Ivorybill on his or her life list. However, if you asked us off the record for our own personal unscientific feelings, I think you would hear several confessions that indeed, some of us do strongly suspect that there has been at least one of these critters tormenting and taunting us in the delta woods for the last several years. Which means we also think that all that follows from this about habitat, behavior, distribution, etc. should be given serious consideration. Interconnected mosaics of fragmented second growth bottomland forest should be included within the spectrum of possible habitats for the species. You will not get anyone involved in the Tennessee project to state that we have established the presence of an Ivory-billed Woodpecker anywhere in Tennessee as a statistical or scientific certainty. None of us has put an Ivorybill on his or her life list. However, if you asked us off the record for our own personal unscientific feelings, I think you would hear several confessions that indeed, some of us do strongly suspect that there has been at least one of these critters tormenting and taunting us in the delta woods for the last several years. Which means we also think that all that follows from this about habitat, behavior, distribution, etc. should be given serious consideration. Interconnected mosaics of fragmented second growth bottomland forest should be included within the spectrum of possible habitats for the species. 

 

 

 


Repost with Addendum: Ivory-billed Woodpecker Sightings and Evidence 1944-2003: The Partially Hidden History

I’m reposting an entry from February 2015 with some new commentary as prologue.

I recently received a Google alert about a new paper on statistical approaches to extinction relying on sight records. According to the paper, which has not yet been peer reviewed:

We have shown that the rate of sightings is the strongest indicator to infer extinction, and too much information about the quality of the sighting can actually be detrimental. Ideally a sighting record would be a list of certain and uncertain sightings only.

I’m curious as to how this model might treat the ivorybill, using the sighting data compiled and analyzed by William C. Hunter in the U.S. Fish and Wildlife Service’s Recovery Plan, a document with which many extinction modelers seem to be unfamiliar.

I’m not trained in statistics, and the literature on this subject is often over my head, but I’m familiar with the concept: “garbage in, garbage out”. Unfortunately, when it comes to the ivorybill, information that is repeated in the statistical papers is often inaccurate:

“For example in 2005, based on a brief sighting and a pixelated image, the ivory-billed woodpecker was declared to have been rediscovered (Fitzpatrick et al., 2005), resulting in the mobilisation of resources for management strategies and recovery plans (Gotelli et al., 2012). However, based on the evidence its rediscovery was brought into question (Sibley et al., 2006), and subsequent extensive searches have failed to result in further sightings (Gotelli et al., 2012).” Roberts DL, Jarić I. (2016) Inferring extinction in North American and Hawaiian birds in the presence of sighting uncertainty. PeerJ 4:e2426c 

An example of a species with a high false detectability is the ivory-billed woodpecker. After 2006, when the US Fish and Wildlife Service offered $10,000 for information leading to an ivory-billed woodpecker’s nest, it was ‘observed’ 14 times and audio recorded 300 times. Nonetheless, the reward remained uncollected (Newton 2009). Lee, T. E. (2014), A simple numerical tool to infer whether a species is extinct. Methods Ecol Evol, 5: 791–796.

Neither of these papers applied the models described to the ivorybill, and I’m not commenting on the validity of the models themselves. I’m pointing to how peer-reviewed literature can sometimes function as an echo chamber in which inaccurate information gets repeated as fact.

While it’s true that extensive searches have failed to obtain indisputable proof, the Luneau video, however controversial, cannot be characterized as a “pixelated image”. There were many more sightings in Arkansas and elsewhere, and in Arkansas, numerous kent-like calls and double knocks were heard and recorded over several seasons.

The book by Newton cited in Lee is Hidden Animals: A Field Guide to Batsquatch, Chupacabra, and Other Elusive Creatures, clearly not a serious scientific treatment of the ivorybill and apparently not a very well-researched one. There were in fact 15 Arkansas sightings between 2004 and 2005 and 14 in 2005-2006. The reward, which was for $50,000, applied to Arkansas only and was offered by the Nature Conservancy, not the USFWS, in June 2006. The source of the claim that audio was “recorded 300 times” is not clear, nor is the meaning. Inaccuracies aside, it’s an enormous logical leap to base an assertion about high false detectability on the inability of an unknown number of bounty hunters to locate a nest in ~500,000 acres of forest.

It may well be true that the ivorybill is more prone to false detectability than some other species; its iconic status makes this seem likely. It’s also true that there have been a number of organized searches for the ivorybill and that the number of sightings has increased as a result of publicity and search activity, at least during the first decade of this century. Nevertheless, many of the records between 1944 and 2003 listed in the USFWS Recovery Plan were unrelated to publicity or organized searches and were incidental to other activities, including bird surveys. In addition, the Recovery Plan tally included some qualitative analysis of the sightings, and an unspecified number of reports were excluded as probable false detections.

I find it odd that Appendix E of the Ivory-billed Woodpecker Recovery Plan is seldom if ever referenced in the recent literature, including Birdlife International’s species account (which I’m honored to say does reference the post below). It’s an official government report and is the most extensively researched document of its kind. I suspect that many readers will be unfamiliar with it and think it merits quoting at length; I’ve bolded some important passages.  I encourage people to click on the link above and read the rest.

Here, a potential encounter is defined as a report not easily explained as something other than an Ivory-billed Woodpecker on the basis of description of the bird, the type of habitat in which it was encountered, and distribution. After the Arkansas announcement was made, post-1944 reports were compiled prior to the 2005 announcement of an Ivory-billed Woodpecker being sighted in Arkansas. A map was produced of these potential encounters in Service brochures. These potential encounters were based on those discussed by Jackson (2004) or otherwise in Service files as “probably reliable,” defined here as not obviously another species. A review of other published literature and files maintained by some State working groups included other potential encounters that are cited and used in this treatment (both before and after 1950). Excluded from further consideration were reports that likely described other species (especially Pileated, but also Red-headed and sometimes other woodpecker species), as well as those reports outside the historical range of the species (as depicted in Tanner 1942) and in unlikely habitats such as golf courses and backyards. The reports between 1945 and 2005 considered further vary in detail, with some accepted based solely on the credibility and reputation of the observer. Reports since April 2005 (i.e., the Arkansas announcement) are similarly treated, but at least one diagnostic field mark had to be observed (most often the white trailing edges on a flying or perched large woodpecker).

It is important to understand the type and level of documentation accepted for this species’ persistence at the time when most collecting of specimens began to trail off (i.e., after 1900) compared with those reports which were accepted without question previously. While most previous treatments break down reports by State, here it is believed that important insights can be made by comparing reports, type and level of documentation, by decade starting with the 1800 and ending with the present. References for those reports besides those of Tanner himself prior to 1940 are provided in Tanner (1942, with cross-reference to location on his maps, his figures 3-10) and are so noted here.

Results and Discussion

The number of locations with Ivory-billed Woodpecker reports peaked between 1880 and 1910, the same period when most specimens were collected (Figures 1, 2). The number of locations with potential reports after 1940 generally dropped below the number of locations with all reports between 1900 and 1940. However, when including only potential encounters between 1900 and 1939, the range in number of locations among decades was roughly similar to the number of locations with potential encounters in the decades between 1940 and 2009, only dropping below 10 locations during the 1990s. The number of locations within each decade with multiple reports among years never exceeded 10 per decade prior to the extensive efforts underway after 2005 to search for this species.

Prior to 1940, only a small percentage of locations from decade to decade provided the source of reports from multiple years within any one decade, ranging from 12 to 28 percent of all locations with birds reported within each decade (Figures 3, 4). After 1940, there was a slight increase in the percentage of locations with multi-year reports in the later decades, ranging from 9 to 51 percent of all locations with birds reported within each decade. Despite this increase in locations with reports from multiple years there was no definitive documentation of persistence at any of these locations. Similarly, a very low percentage of locations with reports spanning more than one decade is documented in the historical record, but again with a slight increase during the latter decades (Figures 5, 6). Reports continue to come from most of Tanner’s regions into the present day with an obvious shift from those regions that included Florida to regions elsewhere (Figure 7).

In summary, there is no evidence that the Ivory-billed Woodpecker was ever widely or consistently relocated in the same areas from year to year or from decade to decade prior to 1940, despite the impression one may have about birds at the Singer Tract during the 1930s. Actually, during Tanner’s study the chore in locating birds often took days or weeks even where pairs or family groups were known to occur from previous years (and actually only one nesting pair at John’s Bayou was consistently relocated during his entire study). Whether the birds were truly more nomadic than previously thought, or whether the low percentage of repeated locations historically has been due to the search patterns of ornithologists and collectors is unclear. What is clear is that the present pattern of reports that do not effectively document occurrence of the species has been repeated from decade to decade for more than a century and that the number of locations with potential encounters within the same decade has varied little since the 1870s.

Whether or not many or all post-1944 reports pertain to actual Ivory-billed Woodpeckers will continue to be debated in some circles, and it also is possible that some of the reports dismissed for purposes of this treatment perhaps should not have been discounted so lightly. However, the pattern of credible-sounding reports accepted for this treatment from locations without firm documentation was from decade to decade slightly lower between 1940 and 2009 than the pattern recorded between 1890 and 1939. Most interestingly, the exceptional increase in locations with potential encounters during the present decade is on the surface similar to what was recorded during the 1930s, given both of these decades experienced a notable increase in amount of effort to firmly document the persistence of this species (with similar results despite substantially fewer observers involved in the 1930s than in the present decade).

RecoveryPlanE1&2RecoveryPlan3-4RecoveryE5-6RecovE7

One caveat about this material: the specific information in Appendix E is potentially subject to change in the future, but the overall patterns are likely to stay similar or the same.

Here’s the February 2015 entry.

This post is inspired in large part by an exchange of emails with Chris Sharpe, an ornithologist who is working on an IBWO literature review. Our correspondence revolved around the IUCN’s species account, which describes the ivorybill as “possibly extinct” and cites recent statistical analyses that suggest extinction is likely, as well as one that indicates survival is possible and another that concludes “very large search efforts are needed to detect small populations.”

Chris pointed out that there are many other species on the Red List that fall into a similar category with many unverified reports but in more remote habitats and nowhere near the search effort that has been expended on the ivorybill. While there’s some validity to this assertion, I think the reality is considerably more complex and that the ivorybill is in fact sui generis.

Many of the specifics of ivorybill history are little-known, and the statistical studies seem badly flawed. One focuses on collection rates but may not adequately address changing attitudes toward conservation in the early 20th century among other factors. Another is perhaps even more problematic for a number of reasons – most importantly its focus on “verified sightings”, which is a particularly complicated issue when it comes to the ivorybill. It omits numerous controversial sightings and does not include post-Singer Tract instances in which physical evidence was obtained, although the authenticity of that evidence has been contested. “Sidewinder” posted the abstract and a good summary of the findings on ibwo.net a few years ago:

Roberts, D. L., C. S. Elphick, and J. M. Reed. 2010. Identifying anomalous reports of putatively extinct species and why it matters. Conservation Biology 24:189–196.

As species become very rare and approach extinction, purported sightings can stir controversy, especially when scarce management resources are at stake. We used quantitative methods to identify reports that do not fit prior sighting patterns. We also examined the effects of including records that meet different evidentiary standards on quantitative extinction assessments for four charismatic bird species that might be extinct: Eskimo Curlew (Numenius borealis), Ivory-billed Woodpecker (Campephilus principalis), Nukupu`u (Hemignathus lucidus), and O`ahu `Alauahio (Paroreomyza maculata). For all four species the probability of there being a valid sighting today, given the past pattern of verified sightings, was estimated to be very low. The estimates of extinction dates and the chance of new sightings, however, differed considerably depending on the criteria used for data inclusion. When a historical sighting record lacked long periods without sightings, the likelihood of new sightings declined quickly with time since the last confirmed sighting. For species with this type of historical record, therefore, new reports should meet an especially high burden of proof to be acceptable. Such quantitative models could be incorporated into the International Union for Conservation of Nature’s Red List criteria to set evidentiary standards required for unconfirmed sightings of “possibly extinct” species and to standardize extinction assessments across species.

Here are the Ivory-billed Woodpecker sighting data they used:

Physical evidence: 1897, 1898, 1899, 1900, 1901, 1902, 1904, 1905, 1906, 1907, 1908, 1909, 1910, 1913, 1914, 1917, 1924, 1925, 1932, 1935, 1938, 1939

Independent expert opinion added: 1911, 1916, 1920, 1921, 1923, 1926, 1929, 1930, 1931, 1933, 1934, 1936, 1937, 1941, 1942, 1943, 1944

Controversial sightings: 1946, 1948, 1949, 1950, 1951, 1952, 1955, 1958, 1959, 1962, 1966, 1967, 1968, 1969, 1971, 1972, 1973, 1974, 1976, 1981, 1982, 1985, 1986, 1987, 1988, 1999, 2004, 2005, 2006

Data were from Tanner (1942), Hahn (1963), Jackson (2002, 2004), Fitzpatrick et al. (2005), Hill (2006), and Floyd (2007).

Some conclusions: For the Ivory-billed Woodpecker, the prior sighting record suggests that even by the time of the first controversial sighting, the species was relatively unlikely to remain extant (ca. 21% chance), regardless of the level of evidence (physical or independent expert opinion) used…the effect on the predicted extinction date will depend on the details of the sighting record. Including controversial sightings will, by definition, move expected extinction dates forward in time. An ever-increasing burden of proof should be required with increasing time since the last verified sighting. The burden of proof also should be greater when there is a pattern of frequent sightings prior to the last accepted record and lower when long periods between sightings are common in the historical record.

A second paper published in 2012 reached the same conclusion using 39 sightings “classified as certain and 29 classified as uncertain”.

The insistence on verification is problematic because it’s founded on an appeal to authority, and for much of the time frame in question, the primary if not sole authority was James T. Tanner. Tanner had a strong predisposition to dismiss every post-Singer tract report he received and was somewhat cavalier about reports he investigated in the late ’30s as well. (In fairness, Tanner did accept a number of post-Singer Tract sightings in an unpublished, late 1980s update to the records section of monograph.)

Tanner likely underestimated the population IBWO population in the late 1930s. At minimum, he missed six pairs in Mississippi, according to Jackson ( In Search of the Ivory-billed Woodpecker, pp. 60-62.  These details reinforce the point made by “Fangsheath” of ibwo.net that, for the ivorybill at least, demanding verification leads to “a rather vicious circularity”. In a recent email, Fangsheath also pointed out that “the Roberts et al. scheme fits tidily into the narrative created by Tanner, that the Singer Tract was the last hope of the ivory-bill, and that when that: wilderness was lost the bird essentially became extinct . . . Tanner searched across several states for the bird and found none elsewhere, yet he himself believed that the bird survived in a number of areas. And so we have a curious contradiction – on the one hand an appeal to authority is being used to exclude many sightings, and on the other hand that same authority is saying the bird exists in areas where sightings are excluded. The mythos that the bird had very specific habitat requirements clouded every search effort and every sighting evaluation, before and after 1944.”

Fangsheath’s observation about the impact of Tanner’s narrative on future search efforts is profoundly important. Tanner’s ideas about habitat, which were in large part a product of his cultural background and the “myth of the frontier”, hardened over time. In later years, he ignored some of the caveats he set forth in his own monograph. But even his approach to reports from the 1930s reflected a set of beliefs about habitat requirements that had no scientific basis. Many people, myself included, are prone to reflexively accepting these assumptions about “habitat quality” because the conventional wisdom is so deeply engrained.

Fangsheath also reminded me that in the years before Tanner, the species was being written off and had been for decades. Florida was believed to be the last stronghold; the Singer Tract and Atchafalaya basin were not considered, nor were the large tracts of overcup oak/water hickory forest (where Beyer found ivorybills in 1898), many of which were untouched until the 1940s. Unlike the Singer Tract, these areas were often roadless and very difficult to penetrate; the Tract was bisected by a road, had few deep bayous, and was largely free of undergrowth, making it much easier to search. I’ve already discussed Tanner’s difficulty in finding ivorybills anywhere besides John’s Bayou. In this context, it’s worth noting that Bick’s 1941 sighting (from his car on Sharkey Road) involved two birds feeding in a lower lying “ash flat” in which overcup oak predominated.

In addition to these conceptual flaws, the papers grossly underestimate the number of post-Singer Tract encounters within the historic range. While it is impossible to quantify the controversial reports, it’s clear that the 26 or 29 referenced in the studies are the tip of the iceberg. There are well over four times that many on record for the 1944-2003 time period. And no doubt, numerous encounters never made it into the literature.

I initially posted a brief comment about this on Facebook and ibwo.net, with a link to Jerome Jackson’s 2002 Birdwatching Daily article listing 20 pre-Arkansas and post-Singer Tract encounters (some just auditory and one from Cuba) and a reference to Michael Steinberg’s Stalking the Ghost Bird catalogue of 85 sightings during the same time frame. A commenter wrote, “Yes but no confirming photos”. That also led me to think it would be worthwhile to explore this subject in a somewhat more depth, since there is physical evidence, albeit contested, related to several post-Singer Tract and pre-Arkansas reports.

Before turning to the physical evidence, it’s worth reiterating that the 1944 date for the last “verified sighting” is fundamentally flawed and arbitrary. The 1944 date is for the “Say Goodnight” encounter that involved artist Don Eckelberry and two local boys, Billy and Bobby Fought, and the purported last lone female IBWO in the Singer Tract. This poignant story was retold in The Race to Save the Lord God Bird, and it has become central to the popular lore about the species. There’s no doubt that the encounter took place, and Eckelberry no doubt believed that the bird was the last of her kind. Roger Tory Peterson apparently received and accepted a report that a single bird, presumably the same one, was still present in 1946. Tanner was likely aware of this and had an additional reason to think that birds persisted in the Tract well after 1944. His papers include a letter stating that Singer Tract game warden Gus Willett saw a pair in November 1948 at North Lake #1 (I have been unable to identify this lake). According to the letter, the “[b]irds are moving over a much larger area than formerly.” The letter mentions that there had been several other sightings during this time period. There’s no reply from Tanner in the archives and no further correspondence about the Singer  Tract birds. It appears that this is the letter from Tanner’s former student, Arthur MacMurray, that is referenced in Jackson, but Jackson’s account does not mention Willett, who would have been familiar with ivorybills. The strong possibility that a pair of birds remained in the Tract for more than four years after it was cut should itself raise questions about Tanner’s narrative.

Jackson’s list of 19 US reports between 1944 and 2003 was undoubtedly not intended to be comprehensive (and his book includes many others). Instead, it focuses on sightings by professional ornithologists and/or people who were familiar with the species. These include: Allan Cruickshank, John Terres, Herbert Stoddard, John Dennis, Davis Crompton (Dennis and Crompton studied ivorybills in Cuba), Whitney Eastman, and William Rhein. Jackson doesn’t mention it, and was perhaps unaware when he wrote the article, but Rhein had filmed the Imperial Woodpecker in Mexico several years prior to his 1959 Florida ivorybill sighting. It strains credulity to think that every one of these experienced observers, most or all of whom were familiar with the species and all of whom knew pileateds well, would be mistaken. Jackson points out that Terres kept his sighting to himself for more than 30 years out of “fear of being scorned.” Such was the climate surrounding ivorybill claims, even in 1955.

Steinberg lists 85 sightings between 1944 and 2003. His list includes most, if not all, of Jackson’s reports, breaking them down into individual incidents. Jackson treated repeat encounters in the aggregate. Nonetheless, most of Steinberg’s reports do not appear on Jackson’s list. Many of them are from less illustrious sources and quite a few are anonymous, but some of them are from game wardens, field biologists, and graduate students in ornithology.

The Ivory-billed Woodpecker Recovery Plan, prepared by the U.S. Fish and Wildlife Service and completed in 2010, includes an even more detailed compilation of records, some of which are of course also included in Jackson and Steinberg. It lists approximately 100 reports of varying quality between 1944 and 2003. Some of these are aggregates, involving multiple observations. The number of observations is sometimes enumerated and sometimes characterized as “numerous”, “multiple”, or “several”, so it’s impossible to arrive at an accurate tally, but the total almost certainly exceeds 150.

Although the Steinberg and the Recovery Plan compilations are more extensive, they are undoubtedly far from comprehensive. For starters, the climate of intimidation around reporting ivorybills was strong enough to deter John Terres in 1955, and that climate of intimidation only grew more toxic over time, as the Big Thicket and Fielding Lewis incidents, not to mention the battle over the Arkansas reports, make clear. In addition, there’s good reason to believe that countless reports from local people, hunters, and amateur birders have been discounted, dismissed, or ignored by authorities, at least prior to the “rediscovery”. Steinberg writes of his first visit to the Louisiana Department of Wildlife and Fisheries Baton Rouge office in 2003,“ . . . few people took the book, or more important the larger issue very seriously. The typical response from many in the office, other than Nancy Higginbotham, seemed to be, ‘Don’t you have anything better to do?’” (Higginbotham claimed two sightings, one of male in 1986 and one of a female in 1987, both in the Pearl River area.) We’re personally familiar with several instances in which reports were dismissed or ignored. One involved the landowner in our old search area, who came forward after the Kulivan sighting and was deeply offended by the way he was treated. As far as I’m aware, no one has done a comprehensive review of records committee submittals within the historic range of the ivorybill; I know of one such submittal from Texas in 2002 that came from unsuitable habitat, outside the historic range, but there may well be others that are more robust.

I’d like to turn to three examples of physical evidence obtained in the post-1944 era. Some of this is fairly well known – the Agey and Heinzmann feather and the Fielding Lewis photographs. The other is somewhat more obscure, but no less interesting for being so.

The Agey and Heinzmann observations took place between 1967 and 1969, in Polk County Florida. They obtained two recordings that Tanner dismissed. There was evidently some very poor communication about it that was compounded by an obvious error on Agey and Heinzmann’s part. They mistakenly thought that calls on their first clip were consistent with some ivorybill sounds from the Singer Tract; they clearly are not. The second clip, which is dominated by a Red-shouldered Hawk, recorded March 3 1968, does have some faint kent-like sounds, but the quality is extremely poor. They are most easily heard on the amplified version that begins at 3:14. The RSHA calls were not what interested Agey and Heinzmann, but they failed to make this sufficiently clear.

I believe Tanner wrote the notes that accompany the recording:

“Well, I’m not sure what to say here. As far as I can determine, there are only four original sound clips here. The recordings at 0:04-0:32 and 0:49-0:57 are certainly flicker-like, especially the continuous series at 0:04-0:21 and 0:26-0:32, but I am less certain about the latter part of the first series (0:21-0:23), which appears to have been recopied twice at 0:41-0:48. A similar vocalization is included at 0:49-0:57 (recopied at 0:59-1:06). Given the very different quality of these sounds relative to those in LNS #6784, combined with the close similarity of the calls to those of Colatpes auratus, leads me to doubt that any of these sounds were given by C. principalis. The recordings from 3 March 1968 (2:45-3:07) represent the calls of Buteo lineatus. Quality unchanged (2;3 – the signal is not bad for the first part, but terrible for the rest, most of which seems to represent copies of various recordings)”

Agey and Heinzmann found several feathers near a cavity, and one was identified as the innermost secondary of an Ivory-billed Woodpecker. Oddly, Jackson wrote that “ . . . some shadow of doubt is cast over these records because Agey and Heinzmann also tape-recorded what they said were Ivory-billed Woodpeckers, and personnel at the Cornell Laboratory of Ornithology identified the birds on those tapes as pileated woodpeckers.” Given that one of the recordings does include kent-like calls, this criticism is not entirely warranted, and the misidentification seems irrelevant in light of the physical evidence (and ironically Tanner seems to have failed to correctly identify the calls on the first clip). Jackson also alludes indirectly to rumors that the feathers were taken from a specimen. These have circulated for years but are unsubstantiated. Agey and Heinzmann published their findings:

Agey, H. N., and G. M. Heinzmann. 1971a. The Ivory-billed Woodpecker found in central Florida. Fla. Nat. 44 (3):46–47, 64.

Agey, H. N., and G. M. Heinzmann. 1971b. Ivory-billed Woodpeckers in Florida. Birding 3:43.

To the best of my knowledge neither publication is available online at this time.

The next event, chronologically, started with a series of encounters in east Texas in the late 1960s. John Dennis obtained a recording that Tanner initially dismissed, in part for the patently absurd reason that a Pine Warbler is also heard on the clip, but later described as “a real mystery” when confronted with the sonograms and analysis that were suggestive of ivorybill. That recording is now catalogued as IBWO.

Additional slides, taken in 1970 in east Texas by a man named Neal Wright, were turned over to the Museum of Natural History in Philadelphia which also houses the Fielding Lewis photographs. These were made public after the rediscovery, and since writing this in 2015, I obtained permission to post them on the blog. They show what appears to be a female Ivory-billed Woodpecker in a nest cavity. When I first viewed the Wright photographs, I was quite skeptical, but later, I was struck by the resemblance to this image from the Singer Tract.

Wright was apparently quite a local character, and I remain somewhat suspicious, as he may have had ulterior motives; however, the similarity to one of the unpublished images from the Singer Tract is strong, and in the pre-internet era, it seems unlikely that a Texas woodsman would be familiar with any of the ivorybill images that did not appear in Tanner’s monograph.

The Fielding Lewis photographs, taken in South Louisiana in 1971, are far better known, although Lewis wished to remain anonymous. His identity was not revealed until more than three decades later, and he was identified at the time only as “the Chief” (Jackson was unaware of his identity in 2004, though it was made public soon thereafter.) George Lowery presented these images at the American Ornithologists’ Union annual meeting and was attacked by many of his colleagues who deemed them to be a hoax. It’s worth pointing out that there have been hoaxes in recent years (these were swiftly and easily debunked), so there’s legitimate reason for skepticism about any claim. In the case of the ivorybill, however, skepticism has frequently been replaced by a virtually irrebuttable presumption of fraud (or error).

In a letter to Tanner, Lowery (who, unlike most of his detractors, had actual field knowledge of ivorybills) wrote: “I know the man in question very well and I am sure he would not pull something like that. In the first place, where would he have gotten the mounted specimen? Why would he have two photographs of the birds way up on two separate trees? Both of considerable diameter and not subject to being shinnied. Also, assuming he might have had a mounted bird to photograph, why didn’t he get a better picture while he was at it?”

The most common reasons given for believing that Lewis hoaxed the photos are that the bird is similarly positioned in both images (similarly but not identically, a neat trick with a specimen) and that the bill and feet are not visible. Bear in mind that these pictures were taken with a Brownie or Instamatic camera, and the quality is very poor. Nonetheless, I believe a foot is very faintly visible in both photos, positioned in a manner that would be expected of a live Campephilus woodpecker. I worked from scans of the originals and made some modest enhancements in Photoshop. Note also that in the first picture, both a cavity and bark scaling can be seen on the tree.

fieldle1-enlarg-scan copylewisphotoarrow

Regardless of whether my analysis is correct, the foundation for claiming that these photographs were faked is shaky indeed – not only for the reasons Lowery gave but also because of Lewis’s reticence about revealing his identity, insistence on keeping the location secret, and lack of any discernible motive.

The recovery plan mentions two other pieces of physical evidence. One is a feather that was purportedly found in a nest or roost cavity in 1985, and the other is a photograph supposedly taken in Georgia in 1975 (correction, 1965).

It’s not my intention to fault the IUCN or to quarrel with the “possibly extinct” designation, although I think Bill Pulliam’s analysis of the Luneau video in light of Rhein’s Imperial Woodpecker film should be dispositive. My main purpose is to call attention to the fact that there’s considerably more evidence for survival than is popularly recognized or than appears in the scientific literature. There are multiple instances of people, often outstanding birders, hesitating to come forward with reports and hard evidence – for decades. Terres waited 30 years; in the cases involving physical evidence, only Agey and Heinzmann went fully public and identified themselves in making their claims; in Stalking the Ghost Bird, Steinberg includes detailed 2005 field notes written by a Louisiana “birder for more than forty years” who “has also worked as a contract ornithologist conducting bird surveys on rice and crawfish farms for more than ten years.” This individual too requested anonymity. To a significant extent, the shortcomings in the literature are directly related to the controversy that has surrounded this species for nearly a century (remember Mason Spencer who went so far as to obtain a permit and kill an ivorybill to prove the species persisted) and the accompanying climate of unhealthy skepticism that has, if anything, grown even more unhealthy since the rediscovery. This sets the ivorybill apart from other possibly extinct species.

I’ll be heading for Louisiana at the end of the week and will post a trip report when I return.


Singer Tract Area Ivorybills in 1948

Just over a year ago, I quoted at length from a 1949 letter to Tanner from Arthur MacMurray (a former student).  I’m reposting that transcript below and have some additional commentary. Eckelberry’s famous “last” John’s Bayou sighting in April 1944 has become a legend, even though Peterson, writing in 1948, had the lone female remaining at John’s Bayou until December 1946.

John’s Bayou aside, the MacMurray letter suggests that at least three ivorybills remained in the vicinity of the Singer Tract until the end of 1948, although not in the areas that Tanner studied. I read these reports as involving at least three birds because Willett mentioned a pair, whereas Williams and McCallip involve a lone bird. The Williams and Willett reports seem highly credible to me, given that Willett undoubtedly knew ivorybills and MacMurray seems to have trusted Williams’s ability to recognize the species.

I have tried to identify the locations involved. Little Fork Road still exists, south of Little Fork Bayou. It is west of the Tensas, about 10 miles northwest of John’s Bayou. North Lake #1 presented a challenge. The only North Lake I could find in the area is the North Lake Marydale Oilfield, which is in Tensas Parish, about 18 miles south-southwest of John’s Bayou and 20 miles south of Little Fork Road, just outside what is now Buckhorn Wildlife Management Area. While it’s possible that MacMurray (via Willett) was referring to a designation on a lumber company map (H. Baldwin, pers. comm.), it seems reasonable to infer that this is the North Lake referenced in the letter.

GoogleEarth_Image

It may be worth noting that as of 1943, a number of relatively small parcels in the vicinity of Little Fork Bayou, including the McCallip property, were not owned by Chicago Mill or Singer. Perhaps these parcels provided at least a temporary refuge, MacMurray’s reference to all he saw having been cut over notwithstanding. Perhaps this hints at how the remaining Singer Tract birds were dispersing or surviving in degraded habitat. Beyond that, there may be little to infer, except that while Eckelberry and the Fought boys’ “last sighting” was valid and makes for a moving story, its lastness is folklore.

***********************************************************************************

The Singer Tract has been cleaned of all its commercial timber as far as I could gather. No Ivorybills have been seen at John’s Bayou for at least three years, according to a resident who has lived adjacent to it for twenty-two years. ( . . . but he is on the lookout for them and remembers you.) John’s Bayou has a lumber railway passing thru it and passing all the way north to some point due west of Tallullah. The Ivorybills apparently left John’s Bayou soon after the large gum tree which had been their nest tree for several years was lumbered.

Mr. Gus Willett is still the local game warden. I phoned him. He expresses his best regards to you. He says that only one pair of Ivorybills are known to be in the region (seen in late November), having moved to North Lake #1. He says that whatever Ivorybills are left are apparently wandering over much larger areas than formerly. He says that all the old stands of gum tree are being lumbered now or very soon, so he thinks the prognosis for Ivorybills is dark and apt to be very brief. He doesn’t know whether or not Ivorybills have been found elsewhere in Louisiana or elsewhere in Florida in the past few years.

A friend of the gentleman who resides adjacent to John’s Bayou reported that he saw what he thought was an Ivorybill on E.C. McCallip’s property on the Little Fork Road 6 miles south of Waverly on December 17th of 1948. So Dot and I spent the night in Tallullah and visited McCallip’s place (minus boots – It was very muddy) All the land we saw looked cut over. There were lots of woodpeckers. Saw 5 Pileateds but none of their cousins. I questioned Mr. Ward Williams (address: Del Hi, Route 1, Box 184-A, Madison Parish, Louisiana) who recognizes Ivorybills and distinguishes between them and the “native” (pileated) peckerwoods. He claims to have seen an Ivory Bill there in November. He regards them as nesting residents and thinks he can find a nest of them there without very much hunting. I left my address, and he intends to write next time he sees a bird. He and his visitors were aware of Ivorybills having been at the Sharkey place adjacent (or in) to Singer Tract.

Dot and I found it expedient under the murky circumstances to proceed on to New Orleans for Xmas day.

. . .

Wish I had more optimistic new regarding the what kind of future we dealt the big-woods peckerwood.

Best Regards,

Arthur

 


Bark: An Exegesis

Introduction:

According to Tanner, scaling bark was the Ivory-billed Woodpecker’s primary foraging strategy during breeding season in Louisiana. Tanner wrote that the ivorybill is “capable of easily scaling away heavy bark that other woodpeckers could not loosen.” (Tanner 1942). All woodpeckers in genus Campephilus have specific anatomical characteristics that enable them to forage in this specialized way (Bock and Miller 1959). Following Tanner, most post-Singer Tract search efforts have looked for feeding sign as an indicator of presence. Because Tanner’s descriptions are somewhat vague and many of the photographs showing feeding sign are poor, these efforts have tended to focus on decay state and bark adhesion without taking bark characteristics and tree species sufficiently into account. I posit that tree species and bark and wood characteristics are key factors that should be considered. I further posit that extensive bark scaling on live and recently dead hickories (genus Carya) may be beyond the physical capacity of the Pileated Woodpecker.

Discussion:

As all regular readers know, I’ve been somewhat obsessively focused on bark and bark scaling since my earliest years of ivorybill searching. The reason for this interest is simple: it’s how Tanner found ivorybills or inferred their presence when he couldn’t find them (Tanner 1942). Unfortunately, as discussed in a number of posts, Tanner’s descriptions are somewhat opaque, and most of the published images of feeding sign, including those in the monograph, are not very illuminating. Indeed, some of them are consistent with pileated work that we’ve documented. Plate 8, shown below, is a prime example. The caption reads, “Ivory-bill feeding sign on a slender limb”.

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Tanner’s Plate 8, Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

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Pileated Woodpecker feeding sign on a slender limb

Early on in my study of this subject, I hypothesized that certain kinds of bark scaling on hardwoods might be beyond the physical capacity of the Pileated Woodpecker. I still believe this to be true, a view that is supported by what we’ve documented for pileated and by numerous examples of pileated scaling from online sources. At the same time, the details of what types of work might belong in this category have shifted somewhat, especially as it has become clear that Pileated scaling can look like what’s shown in Plate 8 and that pileateds will scale bark from recently dead sweet gums.

This is not to suggest that ivorybills never scale small and medium-sized branches in a similar manner. According to Tanner they did so frequently; however, I have been focused on what may be diagnostic for ivorybill. It seems likely that there is considerable overlap between ivorybill and pileated work when smaller branches are involved (at least on sweet gums).

The sequences we obtained showing pileateds scaling a sweet gum limb have inspired me to look more deeply at the characteristics of hardwood bark and pursue some research avenues that I hadn’t considered previously. I’ve linked to some of the sources in recent posts, but I’ve had some additional insights that seem important enough to share. Every time I think I’ve run out of things to say on the subject, something new crops up.

Like virtually everyone else, I’ve followed Tanner and focused on two bark characteristics, “tightness” and thickness, but it recently struck me that other features might be important as well. And the literature, mostly from the lumber industry, supports this idea.

Tanner suspected that the Singer Tract ivorybills preferred sweet gums and Nuttall’s Oaks because the bark is thinner, and the thinner barked limbs had “more borers” than thick barked ones. While abundance of food was likely a factor, I suspect that, at least with respect to sweet gums and possibly Nuttall’s oaks, ease of scaling and access to food played a role.

It’s important to point out that in live trees, hardwood bark adhesion varies seasonally, with bark becoming tighter during dormant stages and looser (with considerably less variation from species to species) during the growing season. Bark is often if not always tighter on recently dead trees than on live ones (Stokland et al. 2012).

In addition, “The structural and chemical traits of dead wood, inherited from the traits of living trees, are also major drivers of wood decomposition and these traits vary greatly among tree species.” (Cornellisen et al. 2012). The authors of the linked paper point out that other factors, including size and site, can also contribute to the way that bark loosens post-mortem, but specific traits seem to be paramount, especially since the scaling we deem to be suggestive, whether on standing or downed wood, is on trees that are alive or are recently dead. Because the scaling has a very distinctive appearance, we also deem as suggestive hickory snags and stubs that appear to have been scaled some years ago, even if they are in a considerably later stage of decay overall. Bark attached to hard wood on these longer dead stubs and snags often remains tight for 3 or more years after death.

A 1978 report, entitled Bark and Wood Properties of Pulpwood Species as Related to Separation and Segregation of Chip/Bar Mixtures examined bark morphology and strength properties in 42 different pulpwood species and identified factors that impede the mechanical removal of bark from logs. These include: cellular structure, bark adhesion, bark strength, bark toughness, wood toughness, specific gravity/density, and moisture content. (Institute of Paper Chemistry 1978) One caveat about this report: a subsequent paper gives the sample size for each species, and in many cases (including sweet gums) it was only 2 (Einspahr et al. 1982)

It may be counterintuitive, but the authors found that shagbark hickory was far and away the most difficult bark to remove. (The tightly adhering layer is thin, beneath the dead bark that gives the species its shaggy appearance.) One key finding was that:

“Morphologically, the presence of fibers increases inner bark strength and, when sclereids (a type of cell) are present, bark strength is decreased. Inner bark strength, in turn, has a major influence on hardwood wood/bark adhesion. The multiple regression equation employing wood toughness and inner bark strength accounts for 72% of the wood/bark adhesion variation encountered.”

Sclereids are virtually absent in hickories (Nanko 1980) and a few other species that don’t approach the hickories in bark strength and bark and wood toughness (Eastern cottonwoods, yellow poplars, white ashes, and black willows). These tables are particularly illustrative:

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woodchart

Shagbark hickories are the extreme outlier in this study, in terms of adhesion, as well as in terms of inner and outer bark toughness and strength; there are very few shagbarks in our search area, and we have never found scaling on one. I have been unable to find specific information about bitternut hickory bark strength or toughness, but the industry’s debarking problem applies to all species in the genus Carya due to the near absence of sclereids in conjunction with the other factors. Moreover, the industry does not differentiate among hickory species (Timber Mart South 2016). This 1996 paper is worth quoting at length in this regard (full text is not readily accessible):

The amount of published literature dealing with hickory debarking is very limited. Often it is only mentioned as an example of one of the hardest tree species to debark. One study quantified this by measuring the strength of the bark-to-wood bond of 42 hardwood species, including hickory. According to Einspahr et al., the dormant season bark-to-wood adhesion for hickory is greater than 3000 kPa, which is a tenfold difference from the growing season and nearly three times as great as the dormant season wood/bark adhesion for quaking aspen (Populous tremuloides, L.), a species considered to be extremely difficult to debark in the northern United States.

Einspahr et al. also microscopically examined the failure zone in an attempt to correlate morphological differences with bark-to-wood adhesion. For hardwoods in general, they found that during the growing season, failure occurred in the cambium or in the xylem just inside the cambial zone. Conversely, dormant-season failure occurred in the inner bark. They also found that fibers in the bark increased the inner bark strength while sclereids decreased inner bark strength. Hickory bark can contain between 15 to 20 percent fiber and contains less than 0.05 percent sclereids.

While these studies have confirmed that hickory is difficult to debark, they have not addressed possible solutions to the problem. As a result, hickory is often left behind during harvesting, reducing the total usable fiber from a given stand and, over time, increasing the percentage of the species in the hardwood resource, compounding the problem of future harvests.

When a tree dies, the bark eventually loosens and detaches naturally as the cambium decays. After felling, the cambium remains alive until it has consumed all available food or dries out. Moisture loss, while causing cambial death, initially greatly increases the strength of bark attachment because additional bonding between fibers occurs as the secondary valence bonds with water are broken (Belli 1996).

Thus, even though hickory bark adheres less tightly than sweet gum bark during the growing season, it seems likely that it’s harder to scale year round, given its much greater wood and bark strength and toughness. It is also clear from my observations that sweet gum bark loosens far more rapidly than hickory bark post mortem. Note that we have found fresh scaling on both live and recently dead hickories.

Based on specific gravity of the bark – averaging 0.72 for shagbark and 0.60 for bitternut – and bark moisture content – averaging 34% of dry weight for shagbark, and 60% for bitternut – it seems likely that bitternuts are somewhat easier to debark than shagbarks but considerably harder to debark than virtually any other tree species in our search area.

Comparing bitternut hickories to other species, most oaks have a considerably higher average moisture content in their bark (Chestnut and Southern red, including Nuttall’s oaks, are exceptions) and similar specific gravities. Sweet gum bark has an average specific gravity of 0.37 and an average moisture content of 91% of oven dry weight. (Schlaegel and Willson 1983, Miles and Smith 2009). But oaks and sweet gums have sclereids, and sweet gums and all tested oak species score far lower on bark toughness and strength than shagbark and, by inference, bitternut hickories. Sweet gums and the tested oak species are fairly similar in these regards, but I suspect that the higher density and lower moisture content in oak bark makes it harder to scale and may mean that oak bark adheres more tightly than sweet gum bark for a longer period after death.

I posit that when it comes to woodpecker scaling, dormant season bark adhesion, inner and outer bark strength, and inner and outer bark toughness are all relevant factors. We know that Pileated Woodpeckers remove sweet gum bark with some difficulty and that even on medium-sized limbs, they are not consistently able to remove bark cleanly down to the sapwood. It’s also clear that bitternut hickory bark is very difficult to remove, second only to shagbark hickory in our search area. This further reinforces my view that the work on hickories is not the work of Pileated Woodpeckers.

Click here and here for examples of the hickories that are scaled in a manner we hypothesize is diagnostic for Ivory-billed Woodpecker. Also be sure to watch this YouTube video of a Crimson-crested Woodpecker (Campephilus melanoleucus) foraging. (Thanks to Phil Vanbergen for finding the clip and the scaled hickory at the second link.) I’m reposting the link to the video here because I think it very clearly illustrates many of the characteristics we associate with Ivory-billed Woodpecker work on hickories, although the species of tree being fed on is unknown. Note the striking similarity in appearance and also that the work of the substantially smaller billed Crimson-crested is not as clean around the edges as the work we’re ascribing to ivorybills.

There were no bitternut hickories in the Singer Tract, but there were congeners – pecans and water hickories. Tanner observed ivorybills scaling on these species twice and digging once. For pileateds, there were 4 instances of digging and none of scaling, as opposed to 5 scaling and 9 digging on sweet gums. The relative abundance of water hickory and pecan at Singer was 2.7%; approximately 10% of the trees in our search area are hickories, and hickories are second only to sweet gums in terms of the number of scaled trees we’ve found. While Tanner’s is obviously a minuscule data set, it may support the hypothesis that live and recently dead Carya bark is too tough for pileateds to scale extensively, if at all.

There are a number of hardwood species found in potential ivorybill habitat that are somewhere between sweet gums and hickories in terms of how easily scaled they may be and how soon after death bark decay and loosening set in – eastern cottonwoods, black willows, water tupelos, some oak species, red maples, green ashes, honey locusts, persimmons, and elms – in these species, it seems likely that close examination of the scaling and bark chips can provide some clues.

Conclusion:

Previous Ivory-billed Woodpecker searches have focused on bark adhesion and state of decay when considering scaling as possible foraging sign. Bark morphology, dormant season adhesion, inner and bark outer strength, and inner and outer bark toughness, and wood toughness are all relevant to the ease with which bark can be scaled from live and recently dead hardwoods. Specific gravity and moisture content are also factors. Bark from trees in the genus Carya is difficult to remove industrially, and members of this genus are likely the most difficult trees to scale throughout the historic range of the ivorybill. Since Pileated Woodpeckers scale sweet gum branches with some difficulty and do not consistently remove bark down to the sapwood, it may be beyond the physical capacity of Pileated Woodpeckers to scale hickories extensively and cleanly, while leaving large pieces of bark behind. Extensive work on hickories that has a distinctive appearance may be diagnostic for ivorybills; this distinctive appearance of this scaling may also be the key to recognizing Ivory-billed Woodpecker foraging sign on other species.

Lagniappe:

This may be no more than an aside, but it may be a relevant data point. I recently observed a Pileated scaling briefly on a live 14″ DBH Norway maple in my yard near New York City. The photos show that the sap is flowing. The appearance of the scaling is exactly what I’d expect for Pileated, with strips about half an inch across. Norway maple may be a decent stand-in for sweet gum; while its bark has a higher specific gravity, 53 as opposed to 37, the moisture content of the bark is almost identical, 91% as opposed to 90%.

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References Cited:

Bock, Walter J. and Waldron Dewitt Miller, The Scansorial Foot of the Woodpeckers, with Comments on the Evolution of Perching and Climbing Feet in Birds, American Museum Novitates, #1931, 1959

Belli, Monique L., Wet storage of hickory pulpwood in the southern United States and its impact on bark removal efficiency, Forest Products Journal. Madison 46.3 (Mar 1996): 75.

Cornelissen, Johannes H.C., Ute Sass-Klaassen, Lourens Poorter, Koert van Geffen, Richard S. P. van Logtestijn,Jurgen van Hal, Leo Goudzwaard, Frank J. Sterck, René K. W. M. Klaassen, Grégoire T. Freschet, Annemieke van der Wal, Henk Eshuis, Juan Zuo, Wietse de Boer, Teun Lamers, Monique Weemstra, Vincent Cretin, Rozan Martin, Jan den Ouden, Matty P. Berg, Rien Aerts, Godefridus M. J. Mohren, and Mariet M. Hefting, Controls on Coarse Wood Decay in Temperate Tree Species: Birth of the LOGLIFE Experiment, Ambio. 2012 Jul; 41(Suppl 3): 231–245.

Einspahr, D.W, R.H VanEperen, M.L. Harder et al. Morphological and bark strength characteristics important to wood/bark adhesion in hardwoodsThe Institute of Paper Chemistry, 1982: 339-348.

Institute of Paper Chemistry, Project 3212, Bark and wood properties of pulpwood species as related to separation and segregation of chip/bark mixtures, Report 11, 1978.

Miles, Patrick D. and W. Brad Smith, Specific Gravity and Other Properties of Wood and Bark for 156 Tree Species Found in North America, United States Department of Agriculture, Forest Service. Northern Research Station, Research Note NRS-38, 2009.

Nanko, Hiroki, Bark Structure of Hardwoods Grown on Southern Pine Sites (Renewable Materials Institute series), Syracuse University Press, 1980.

Schlaegel, Bryce E. S and Regan B. Willson, Nuttall Oak Volume and Weight Tables, United States Department of Agriculture, Forest Service. Southern Research Station, Research Paper SO-l 86, 1983

Siry, Jacek, ed., Species Detail Report, Timber Mart-South, 2016

Stokland, Jogeir N., Juha Siitonen, and Bengt Gunnar Jonsson, Biodiversity in Dead Wood, Cambridge University Press, 2012

Tanner, J.T. The Ivory-billed Woodpecker,National Audubon Society, 1942.

Thanks to Fredrik Bryntesson, Steve Pagans, Chris Carlisle, and Bob Ford for their help with this post.