Bits and Pieces Part 5: More on Range and Habitat Variety
Posted: December 22, 2017 Filed under: Habitat, Ivory-bill History, Old Growth | Tags: Arkansas, Barrier Island, bottomland forest, florida, habitat, historic range, IUCN, Ivory-billed Woodpecker, James T. Tanner, Louisiana, Missouri, old growth, Pileated Woodpecker, Singer Tract, South Carolina, Upland 1 CommentI 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; Matt Courtman blamed this tendency on internalized beliefs. And for my part, I sometimes find it hard to shake these beliefs.
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.
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.
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:
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.
Back in October, Matt Courtman discovered that 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.
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 3: Internalized Beliefs, How They Got That Way, and What the Record Really Shows
Posted: October 9, 2017 Filed under: Ivory-bill History, Old Growth, Uncategorized | Tags: bald cypress, Canadian River, Cimarron River, cottonwood, habitat, Ivory-billed Woodpecker, James T. Tanner, oklahoma, old growth, Texas, willows Leave a commentPart 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.
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.
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.
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. 
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.
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.
Go Read Bill Pulliam’s Blog While You Can
Posted: September 14, 2017 Filed under: Ivory-bill History, Uncategorized, Updates | Tags: Beaver, Bill Pulliam, Campephilus principalis, double knock, Ivory-billed Woodpecker, James T. Tanner, kent-like calls, Louisiana, Luneau video, Moss Island, old growth, Tennessee Leave a commentI 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.
Insights, Ants, and Old Growth: a Nuanced View of the Ivorybill’s Decline and Possible Survival
Posted: July 11, 2016 Filed under: Habitat, Ivory-bill History, Old Growth, Uncategorized, woodpecker anatomy | Tags: adaptation, Bark Scaling, behavior, Campephilus, Campephilus principalis, cerambycids, feeding, foraging, Ivory-billed Woodpecker, James T. Tanner, John's Bayou, Louisiana, old growth, Pileated Woodpecker, Singer Tract Leave a commentI’ve just finished reading Tanner’s dissertation and have gained some new insights into topics that have been discussed in a number of earlier posts.
Conventional wisdom, following Tanner, holds that the Ivory-billed Woodpecker’s decline and possible extinction were caused by habitat loss, specifically the logging of old growth forests during the 19th and early 20th centuries. Birdlife International’s fact sheet on the species suggests “that large contiguous tracts of mature woodland would be required to support a viable population”, referencing Jackson 2002. Snyder et al. have proposed an alternative hypothesis that “human depredation was the primary factor.” (p.9).
Tanner’s model depends on the idea that food supply was the limiting factor on ivorybill populations, because the species is highly specialized, and that old growth conditions were optimal or essential. While Tanner was aware that ivorybills bred successfully in an area that was predominantly second growth, at Mack’s Bayou, he glossed over this fact in the monograph, and became more dogmatic about old growth as a requirement in later years.
Snyder and some others have contended that the ivorybill is a generalist. According to Snyder, “the data available on diet and foraging methods simply do not provide compelling evidence for strong feeding specialization.” Snyder goes on to suggest that “[i]ts apparent skill in exploiting recently dead timber, coupled with its ability to feed in a variety of other ways, may even have given it some significant foraging advantages over the pileated woodpecker, a species apparently much less capable of bark stripping. Indeed, the pileated woodpecker, like other Dryocopus woodpeckers, may well be more of a food specialist than any of the Campephilus woodpeckers.” (p. 37).
As I see it, there are elements of truth in both models, but neither is complete. In addition, I think that each model relies on at least one flawed premise.
The old growth/virgin forest component of Tanner’s model fails to account for the facts that the Singer Tract population was dwindling even before logging began in earnest and that birds appear to have remained in the Tract until well after it had been extensively logged. Tanner suggested another possibility, “perhaps the greatest factor reducing the rate of ivorybill reproduction is the failure of some birds to nest. One reason for their not breeding is immaturity, for it is probable that ivorybills do not nest until they are two years old. Another possibility is that the quantity of food available to the woodpeckers may determine whether they will nest or not.” (p. 83).
Tanner struggled to account for the fact that the ivorybill population at Singer was dwindling by the mid-1930s, even though overall habitat quality had, if anything, improved relative to what it had been a few decades earlier. He attributed the higher relative abundance in previous years to tree mortality due to fires that took place in 1917 and 1924. Tanner also recognized the probable importance of fire in the pre-contact era, although he seems to have been unaware of the ways pre-contact Native Americans used fire, both for agriculture and habitat management. (The impacts of Native American fire use were almost surely different from what occurred in the 20th century Singer Tract).
Neither Tanner (whose study predates the emergence of the discipline) nor Snyder, take environmental history sufficiently into account. There had been major ‘changes in the land’ long before large scale logging began in the southeast and before the reports of local abundance on which Snyder relies. These changes include: the post-contact collapse of Native American civilizations, the introduction of European plant and animal species, the clearing of log jams on major and secondary North American rivers, habitat fragmentation due to the plantation economy, and the near extirpation of the beaver.
All of these elements likely contributed to a major decline in ivorybill populations. Ivory-billed woodpeckers likely concentrated locally in response to major disturbances, regardless of whether forests were old-growth or advanced second-growth, and this type of specialization caused birds to congregate, making it easier for collectors to kill them in large numbers in short periods of time. Snyder likely misinterpreted this collection of large numbers of Ivory-bills in short periods of time as reflecting a greater regional abundance. In contrast, and more consistent with Tanner, this ecological response to disturbed areas led, in some places, to the collectors extirpating regional populations.
In the latter part of the 19th century, hunting probably sped the collapse of the remaining population, but Snyder’s claim that available data on diet and foraging methods do not provide compelling evidence of specialization fails to account for the anatomical and other evidence that suggests otherwise. It also fails to account for the Pileated Woodpecker’s far more extensive range and ability to thrive in a wider variety of habitats, including badly fragmented and degraded ones. I made some of the case for specialization in a series of recent posts, but there’s more to add, especially with regard to ants.
In one of those posts, I hypothesized that the inability to exploit ants as a food resource was a key component, perhaps the primary component, in explaining the decline of the ivorybill. A commenter asked whether there’s evidence to support the idea that ivorybills and other Campephilus woodpeckers don’t feed on ants and also whether there’s evidence to support the idea that Campephilus woodpeckers don’t regurgitate.
Adult Campephilus woodpeckers rarely feed on ants but do not feed them to their young. They make frequent trips to the nest with food items stored in the bill or at the back of the bill. (M. Lammertink, pers. comm.) Dryocopus woodpeckers and those in closely related genera (the “tribe” Malarpicini) feed their young by regurgitating, while other woodpeckers do not. (Manegold and Topfer, 2012). I think the capacity of Pileated Woodpeckers to consume ants in large quantities and to feed them to their young is a significant distinguishing factor and that Tanner was correct in suggesting that food supply was a major limiting factor on Ivory-billed Woodpecker populations.
Ants comprise up to 33% of the world’s terrestrial animal biomass. In Finland, they comprise as much as 10%. In tropical forests, the percentage is much higher, exceeding vertebrate biomass by 400%. Tanner’s comparative analysis of available ivorybill and pileated food did not include ants, so Tanner’s comparative estimate of available insect prey – suggesting that pileateds in the Singer Tract had access to approximately four times what ivorybills did – was in fact extremely low.
Tanner’s dissertation concludes with a discussion of Audubon’s ivorybill dissection, something that was omitted from the monograph. While I had a passing familiarity with the Audubon material, I had not looked at it carefully. Nor had I compared his ivorybill and pileated dissections.
Tanner wrote: “The proventriculus is both muscular and glandular. Audubon’s drawings and text indicate that the proventriculus of a Pileated is much larger in proportion to the stomach than is the case in the Ivory-bill.” Audubon described the ivorybill proventriculus as being only minimally wider than the esophagus. By contrast, the pileated proventriculus as “an immense sac, resembling a crop, 2 1/4 inches in length and 1 and 5 twelfths in width,” or nearly three times as wide as the esophagus.
Audubon’s drawing of Ivory-billed Woodpecker digestive tract showing slightly widened proventriculus.
Audubon’s drawing of Pileated Woodpecker digestive tract showing large, sac-like proventriculus.
The proventriculus and stomach of one of Audubon’s specimens contained “a vast mass of ants and other insects”. According to Bent, Beal found one pileated stomach that contained 2,600 ants. (Others contained fewer, 153 and 469, according to Sutton.) Thus, it’s clear that even if ivorybills sometimes ate ants, they lacked the capacity to consume them in large quantities, let alone feed them to their young.
This supports Tanner’s view that specialization was a limiting factor on ivorybill populations. I’ve previously suggested that this might apply only to breeding season, but it seems reasonable to infer that it’s a factor year-round, based on the differences in proventricular structure.
All of that said, I’d argue that this specialization should not necessarily be read to include dependence on large tracts of mature, contiguous forest. The data from the Singer Tract suggest that even under these ‘optimal’ conditions, breeding was limited. And the fact that the Mack’s Bayou birds bred successfully in an area of second growth suggests that birds could thrive under ‘suboptimal’ conditions. The extent to which survival might be possible in fragmented habitat is less clear, but Snyder (citing Jackson) refers to the Mississippi population of six pairs in a 19.2 square mile forest that Tanner missed; the tract is less than 1/6 the area of the Singer Tract and is smaller than many contemporary wildlife management areas.
The tract, known as Allen Gray Estate, was west of Skene, Mississippi in Bolivar County; some or all of it is now part of Dahomey National Wildlife Refuge; the US Fish and Wildlife Service Habitat Management Plan for the refuge (2013) states that the forested portion of the refuge comprises 8100 acres and provides this historical information, “Dahomey NWR is located on the grounds of the old Dahomey Plantation founded in 1833 by F.G. Ellis and named after the homeland of his slaves. Much of the land west of the refuge was probably cleared for cultivation around this time. The land went through several owners and was purchased by Allen Gray in 1936. The portion that became the refuge was known as the “Allen Gray Woods”. This was the only significant portion of the plantation still forested.” This 8100 acre figure is 25% lower than the figure reported by Jackson and Snyder.
While I have been unable to find a detailed logging history of Bolivar County, it is in the heart of the Mississippi Delta, which was known for its plantations. Between 1900 and 1940, Bolivar County was more densely populated than Madison Parish: 39.1 people per square mile as opposed to 18.9 in Madison Parish in 1900, 78.92 as opposed to 22.78 in 1930, and 74.57 as opposed to 28.33 in 1940. Based on population density and the number of towns, it seems self-evident that the habitat in Bolivar County was considerably more fragmented than was the Singer Tract.
Thus, there is good reason to question Tanner’s old growth model as well as the idea that large contiguous tracts of mature forest are required. Similarly, there’s good reason to question Snyder’s argument that hunting rather than specialization was the primary cause of the ivorybill’s collapse.
Efforts to reintroduce the beaver in the southeast began in the 1930s, and the population has been growing ever since. Beavers injure trees by partially or fully girdling them and by altering hydrology, which weakens or kills trees at the edges of the ponds they create. Beaver damage renders trees more vulnerable to infestation by ivorybill prey species, something we’ve observed repeatedly in our search area. In Tanner’s day and in the late 19th century, the beaver was barely a part of the southeastern ecosystem, but by the 1950s, beavers again were playing a role in altering southern forests, whether mature or successional.
If the ivorybill was able to survive the logging of the last large tracts of old growth forest, as I think it was, the reintroduction of the beaver may have been central to its persistence. If this hypothesis is valid, there is considerably more potential habitat today than there was in Tanner’s era; much of this potential habitat has been overlooked or dismissed in organized search efforts; and the dismissals of post-Tanner reports based on his habitat model rely, at least in part, on a false premise.
Old Material, New Light: More from the Archives Part 1
Posted: May 7, 2016 Filed under: Cavities and Feeding Sign, Ivory-bill History, Uncategorized | Tags: Bark Scaling, behavior, Campephilus, feeding sign, Ivory-billed Woodpecker, James T. Tanner, Louisiana, old growth, Singer Tract 2 CommentsI’m planning to do a few more posts drawing on material I’ve found in Kroch Library’s Rare and Manuscript Collection at Cornell. There may be an intervening post or two on other topics.
While Tanner’s monograph is well-known, the reports he wrote for the Audubon Society at the end of each season are not publicly available, except in the archives. The contents of these reports call some conventional wisdom about the species into question.
First and perhaps least important, it seems to be commonly believed that the John’s Bayou birds were the only remaining ivorybills in the Singer Tract when Tanner visited in December 1941. They were indeed the only birds he saw, as noted in his report (the first document below); however, he found feeding sign in the Mack’s Bayou area and suggested that at least two more birds remained, one at Mack’s Bayou and another in Greenlea Bend. As I read the report, Tanner referenced Bick’s observation in August ’41 (discussed here), and the context suggests that he related it to the John’s Bayou family. Other interpretations are possible, including that this was another family group that was passing through the area, which would mean that the remaining 1941 population was even larger.
In Ghost Birds, Steven Lyn Bales provides a full accounting of Tanner’s population estimates, but earlier books by Hoose and Jackson gloss over the likely presence of the other birds. Hoose (p. 120) wrote that James and Nancy Tanner “maybe heard a third” at Mack’s Bayou. (The source of this information is not identified.) Jackson (p. 132) has Nancy Tanner seeing a male and a female in December 1941. Both Bales and Hoose are clear that she saw the pair in 1940; per Bales, the actual date was December 21.
While there’s no way of knowing whether the birds Bick saw were the John’s Bayou family, I suspect that they were. I also think it’s reasonable to infer, as Tanner did, that this group bred successfully in 1941 (possibly an important point given the disturbance to the habitat). If Bick’s birds were the ones from John’s Bayou, it seems the male disappeared sometime between mid-August and December. Given the consistent presence of this family group in the vicinity for nearly a decade, there’s perhaps a hint of wishful thinking in Tanner’s suggestion that the male “might have moved away” due to the logging.
The next interesting tidbits come from a 1938 interim report that Tanner sent to the Audubon Society, under the terms of his fellowship (the document below and accompanying map). The report includes a reference to a non-breeding pair in the Mack’s Bayou area. This pair does not show up in Tanner’s published counts, either in the monograph or in his dissertation. It seems possible that Tanner concluded the pair that was seen around Mack’s Bayou and the pair with two young that Kuhn found later were one and the same, erring on the side of caution in his final population estimates.
What stands out in both of these documents is the difficulty Tanner and Kuhn faced when trying to find ivorybills other than the John’s Bayou family. This is a topic I’ve touched on in several other posts because of the common belief, fostered by Tanner in later years and advanced by many 21st-century “skeptics”, that ivorybills should be easy to find.
During his brief, two week visit in 1941, Tanner couldn’t get to Greenlea Bend at all and didn’t find the Mack’s Bayou bird, although he found evidence that it was still there. The 1938 report illustrates how hard it was to find ivorybills even more explicitly. Kuhn and Tanner were unable to locate a pair that had been seen by others in a fairly circumscribed area, although it’s possible that Kuhn happened on this pair and the young of the year on June 15th.
Beyond that, it took Tanner and Kuhn “two or three weeks” to find an ivorybill in an area where there was “an abundance of feeding sign”, and Kuhn only found the bird in question by following it to the feeding sign from a known roost. It seems that, while ivorybills may sometimes have been “noisy and conspicuous”, they were for the most part quite the opposite.
Materials are courtesy of the Division of Rare and Manuscript Collections, Cornell University Library.
Trip Report: February 5-11, 2016 and More on the Singer Tract
Posted: February 20, 2016 Filed under: Cavities and Feeding Sign, Habitat, Ivory-bill History, Old Growth, Trip Reports, Uncategorized, Updates | Tags: Auditory Encounters, Bark, Bark Scaling, behavior, Camera trap, Campephilus, feeding sign, Frank Wiley, Ivory-billed Woodpecker, James T. Tanner, Louisiana, old growth, Pileated Woodpecker, Project Coyote, Singer Tract, sweet gum 1 CommentI flew into Houston on February 4 and arrived at the search area on the morning of the 5th. Frank’s work schedule had precluded him from returning to the search area during my absence, and he was unable to get time off to join me this trip.
Tommy Michot visited on the February 5th; we went to the northern sector, and passed the downed sweet gum top (actually a limb) found in April of last year. Project Coyote had a camera trained on it for some time but took it down due to equipment failure. The main stem, which reaches from the ground to about 20 feet up, had been scaled extensively, down to the base, over the course of the last month. Some of the work had been done no more than a few days prior to my arrival based on the condition of bark chips found at the base.
We have a camera back on this top but have low expectations, since so much bark has been removed that it makes a much easier target for other species of woodpecker. While I don’t believe in the “curse of the ivorybill”, individuals and small groups of self-funded searchers face enormous obstacles and are dependent on equipment that’s often unreliable.
Tommy and I measured a number of the largest trees in the area, and the biggest oaks and sweet gums are around 4’ DBH, with many more in the 3’ range. Here are some of the highlights: two Nuttall oaks: 137 cm/53.94”, 119 cm/46.85″; swamp chestnut oak 110 cm/43.31” four sweet gums: 124 cm/48.82”, 123 cm/48.43”, 110 cm/43.31″, 109 cm/42.91”.
While ours was not a random sample, this table from a 1986 paper by Tanner (on data collected in the Singer Tract in 1938), is interesting for the sake of comparison.
In his 1944 report on the Singer Tract, Richard Pough described sweet gums in the 5’-6’ DBH range as being characteristic of old growth conditions, and such trees were not uncommon in the 19th century. Impressionistically, at least, most of the ~4’ DBH sweet gums in our area are moribund and are likely to have lost their tops. I know of only one gum that appears to be in the 5′ DBH category. As of 2009, the national champion sweet gum had a DBH of 5’4.6″. The tree below could be close to that.
Frank Wiley with massive sweet gum
Many, perhaps most, gums have at least some beaver damage. This may be contributing to the earlier mortality, both by stressing the trees directly and by creating the opportunity for beetles to infest them. I have long suspected that the decline of the beaver could have contributed to the IBWO’s disappearance, since beavers directly damage trees by gnawing and also stress or kill them by altering hydrology.
124 cm dbh sweet gum with beaver damage at the base, measured this week. The photo was taken in 2013, and the top of the tree has fallen in the interim.
Beavers were extirpated from much of Louisiana by the early 19th century. As of 1931, populations were restricted to the Amite and Comite rivers in the southeastern corner of the state; they were reintroduced in other areas in 1938 and had established themselves in 21 parishes as of 1951. (Wylie Barrow, pers. comm.) Range expansion continued into the 1990s and after. They’re now considered a pest animal and appear to be found in all parishes. A recent paper suggests that the introduction of beavers into Magellanic Woodpecker habitat may have benefitted that species.
I was on my own on February 6th, and I went and staked out the downed top for the better part of the morning. Nothing landed on it except for a Red-bellied Woodpecker that pecked and gleaned but did not scale bark or do any excavating. At approximately 9:30, I did a very aggressive series of ADKs. I heard a couple of loud single knocks that seemed to come from no more than a couple of hundred yards away and also a possible double knock. These came during a period when I was standing, moving around, and doing the ADKs, so I did not hear them very well. In addition, there were a few distant gunshots within about 15 minutes after the series, so I’m not very confident about what I heard. (These were the only shots heard all day.) I found some scaling the next day a couple of hundred yards away (discussed below). This gives me some reason to think the SKs were a reaction, not shots. Still I’d place these in the weak possible category.
One highlight of the day was watching a pair of Red-shouldered Hawks in the act of mating.
I returned to the same area on the 7th, with two cameras to deploy. One is aimed at a large sweet gum stub, about 20’ tall and well over 3’ DBH that I found last trip. The top had broken off shortly before my arrival. While it’s not discussed in Tanner, T. Gilbert Pearson, who was the first modern ornithologist to observe the Singer Tract IBWOs, described this type of “stump” as one of the species’ preferred feeding sites. This is a tree on which I found high branch scaling last year, before the top broke off. I expect this to be a long-term deployment.
I also redeployed a camera on the downed top, although we’re not very hopeful about that location, since the scaling is so extensive and the bark has been loosened in many of the remaining unscaled areas.
I walked south for a couple of hundred yards and found very fresh, large bark chips at the foot of a live sweet gum (there were two large gums ~3’ dbh about 10’ apart). There was extensive scaling on live or recently dead high branches of one or both of these trees. Because there had been a major rainstorm and accompanying minor flooding a week before and the chips were mud free, I can be sure the scaling took place after the rain, and since Tommy and I had spent considerable time in the area examining some other nearby scaling two days before, I strongly suspect this work was done on the 6th. I can’t help but wonder whether the possible single knocks came from whatever was doing the scaling; that would be consistent with my immediate impression when I heard them, both in terms of distance and direction. Nonetheless, my confidence level about the SKs is low given the gunfire.
I don’t think the scaling and bark chips are consistent with squirrel; the chips are large and thick and do not show signs of having been chewed off; the ones collected weighed over five pounds.
There was a little excavation and exit tunnel expansion (visible in the first image above) associated with the scaling; and it has the generally clean edges and lack of layered, flaked off appearance around the edges or on the chips. The leaves and gumballs are attached on most of the limbs, indicating that they’re alive or very, very recently dead, so the bark is almost certainly tight. This is about as good as it gets when up-close examination is not an option
I met Tom Foti, who came in from Arkansas, on the morning of the 8th. Winds were high, with gusts approaching 50 mph. We decided it would be unsafe to venture into the woods, so we drove around the edges of the search area looking at the surrounding upland forest, much of which is impressive and mature. Tom is very enthusiastic about the area, ivorybills or not, and we’re hopeful that steps will be taken to protect and manage it appropriately. The car ride was a running lesson on southern forest ecosystems, and as I told Tom, I’ll count myself lucky if I retain 10% of what I learned.
The next morning, the winds had dropped enough to make it safe to head for the swamps, and Tom and I visited the southern sector, an area where we haven’t spent much time lately. As mentioned in some previous posts, there has been a significant uptick in four-wheeler activity in the area, and it’s heartbreaking to see the destruction these callous individuals are causing. Fortunately, the damage is almost entirely limited to the periphery, and the deeper parts of the bottom are unscathed. The habitat types here are somewhat different, and the logging date is more recent, but it remains very impressive. We walked a long way and went to places I had never been, including a lower-lying flat with tree species I haven’t noticed elsewhere – shagbark hickory, bitter pecan, and overcup oak.
We saw no recent feeding sign in any of these areas, except for some older work on a small sweet gum that I described as being about a grade B-.
We then looped back along a different track, passing the spot where I recorded calls in March of 2013 and where we’d had a concentration of feeding sign in 2012 and 2013. We found nothing until we reached a location farther north that is within 100-200 yards of the tree shown on the homepage. Tom spotted a group of trees with bark scaling, some on boles and some on branches. Once again, this was not “grade A” work, but the concentration makes it more interesting than if it were one isolated example. We did not find any chips at the base of the snag that had been scaled on the bole, and the high branch work is not as extensive some.
It’s worth pointing out that on many days, I’ll walk for hours and see nothing and then find either a dramatic example of scaling or a small cluster of it. Tom and I had probably walked 3.5 miles or more before finding this little cluster.
I was on my own again on the 9th, and I opted to go on a death march to retrieve a trail cam from a tree deep in the swamp and proceed north from there. The tree is a large blown down sweetgum discussed and shown here. There was some fresh scaling on it that I suspect was done by a Pileated Woodpecker. There are nearly six weeks of images to go through, so it will take some time before we find out if there were any captures.
As on the previous day, I walked for a couple of hours without seeing or hearing anything suggestive until I got to a part of the area we haven’t visited since last year, perhaps a quarter mile south of the southernmost point Tommy and I had reached earlier in the week. I found old sign, some of which was fresh last winter and some of which was older. I then found some fresh work on two trees in close proximity to one another. Some of the scaling was on a downed tree but was clearly done by a woodpecker, with chips and other characteristics that I consider to be suggestive. Since the chips were caked with mud, the scaling was a little over a week old. The other work was on one high branch, but conditions made it impossible to look for chips.
Bark chips found beneath downed sweet gum. iPhone shown for scale is 5″x2.5″
On the return hike, I found what I’m quite sure is Pileated Woodpecker work on a recently dead or dying hickory. Since we’ve found a number of hickories that we suspect have been scaled by Ivory-billed Woodpeckers, this was an unusual opportunity to do a direct comparison. In my view the work on hickories is the most compelling for ivorybill due to the density and tightness of the bark and the hardness of the wood. There are pronounced differences in the presumed Pileated and suspected ivorybill work on this species.
The work on the homepage is suspected ivorybill. It is extensive, with huge contiguous areas, perhaps 20% of the entire surface, completely stripped, with evidence of bill strikes targeted at exit tunnels. The Pileated work is spotty by comparison. The bark chunks scaled from the tree on the homepage were large, dense, and thick, and there were no pieces of sapwood among them. By contrast, the suspected Pileated work involves very small pieces of bark that appear to have been removed by digging rather than scaling; there were also a few pieces of punky wood among the chips.
Presumed Pileated Woodpecker work on recently dead or dying hickory
Detail of presumed Pileated Woodpecker work on hickory
Small chips at base of hickory
Different view of scaled dying hickory that appears on the homepage. Work is suspected Ivory-billed Woodpecker
Bark chips from base of hickory shown immediately above
The next morning, I drove to the Wetlands and Aquatic Research Center (formerly the National Wetlands Research Center) in Lafayette and met with Wylie Barrow, Heather Baldwin, Tommy Michot, and Philip and Eric Vanbergen. (Two young enthusiasts who will be helping us out.) Frank joined us briefly, and then Wylie, Tommy, the Vanbergens, and I went out to lunch. It was an exciting and thought-provoking day, and the Research Center is an incredible facility. Wylie and Heather shared their comprehensive and in-depth analysis of conditions in the Singer Tract in Tanner’s day. They’ve amassed an array of materials encompassing land records, Civil War era maps, and stereographic aerial photographs. Their research far surpasses my own speculative effort. It covers the finest details – roads, improved and unimproved, snag densities, tree mortality, conditions around roost and nest sites, as well as conditions in other locations where ivorybills were seen. Tom Foti has done complementary research on hydrology, soils, and vegetation.
Their presentation convinced me that I’ve been too hard on Tanner in some respects. There was a little more old growth in the Singer Tract than I had inferred from the Pough report and some of the historical documents. Nonetheless, the characterization of the Tract as a whole as “virgin” forest is somewhat misleading, since over a quarter of it was second growth, and some of it fairly young. Heather and Wylie have graciously given me permission to summarize some of their findings.
When Tanner began his study, 72% of the Singer Tract was old growth. (Tanner estimated it at over 80%.) Logging in 1938 reduced that percentage to 67%. The ridges, which Tanner deemed to be the best ivorybill habitat, were actually the least likely areas to be old growth. (Tom Foti’s analysis also points to a preference for higher, drier locations.) The regrowth percentages for each landform in Tanner’s day are as follows:
Ridge (43%)
Low ridge (23%)
Total on ridges (32%)
Flat (9%)
Low flat (4%)
Cypress brake (4.5%)
For the most part, the second growth forests were not particularly old, as has been suggested in previous posts. According to Heather, most of these areas only started to regrow in the 1880s and 1890s, “due to consecutive depressions and low cotton prices”. Thus, parts of the Singer Tract were relatively young second growth, and this included one of the ivorybill home ranges and one that Tanner deemed to be “best” – Mack’s Bayou.
The nature of the habitat in the Mack’s Bayou area is immediately apparent from the 1938 aerial photos, which suggest forest conditions that are present in many parts of Louisiana today. Nevertheless, Ivory-billed Woodpeckers nested there in 1934 and 1935, at minimum, and did so successfully at least once. This fact alone refutes the idea that Ivory-billed Woodpeckers are old growth dependent. Heather informs me that there was an abundance of dead and dying trees on the eastern side of the Mack’s Bayou range, due to a fire caused by logging activities. In any event, the home range Tanner delineated in this primarily second growth area is no larger than the home range he delineated around John’s Bayou, which had more mature forest. In fact, the area he designated as “best” for ivorybills around Mack’s Bayou was slightly smaller than its older equivalent near John’s Bayou.
Tanner knew that a significant portion of the Mack’s Bayou home range was not old growth, since his 1941 map shows “old fields” in the heart of it. He seems to have been unaware of the resurgence of cotton growing during the 1870s and 1880s, so he may have overestimated the age of the forest on that basis. I can’t help but wonder if he glossed over the conditions in the Mack’s Bayou range in part for the sake of protecting the Singer Tract and (as Heather suggested) in part based on what he deemed to be best for the birds from a conservation standpoint, an approach that later ossified into a categorical set of beliefs about old-growth dependence.
As I and others have been arguing for years, extensive forest cover, sufficient dead and dying wood, and enough large trees for roosting and nesting are probably the main requirements, even if old growth or near-old growth conditions are optimal.
I plan to return to the search area in late March and have another post or two in mind in the interim.
Scaling and Squirrels: Part 2, Digging Deeper
Posted: January 18, 2016 Filed under: Cavities and Feeding Sign, Uncategorized, woodpecker anatomy | Tags: Bark, Bark Scaling, behavior, Campephilus, foraging, foraging behavior, Ivory-billed Woodpecker, James T. Tanner, old growth, Pileated Woodpecker, Project Coyote, specialization, Woodpecker Leave a commentPart 1 of this series is here, and the event that led to my writing it is discussed here. I now expect to write 2-3 additional posts on this topic and may create a new page that summarizes the whole series. I’ve hidden the Bark Scaling Gallery page to be reworked later or incorporated into the summary.
This post will reiterate, revise, and expand upon earlier ones dealing with bark scaling and woodpecker anatomy. The next one will focus on certain characteristics of the scaling we think is being done by Ivory-billed Woodpeckers, on finer details that characterize it (based in part on comparison with work done by congeners), and on how to differentiate it from bark removal done by squirrels. The following entry will deal with bark chips in more depth, and from a slightly different angle than previous posts on that subject.
I had originally intended to address the next post’s planned content in this one, but as I started writing, I realized the long but necessary introduction would bury the lede. It soon became clear that I’d have to divide the post in two with this one for background.
The first important point is that woodpecker taxonomy is in a state of dramatic change, so much so that the American Ornithological Union is being advised to place Downy and Hairy Woodpeckers in separate genera and that their current genus, Picoides, should be divided into four. Notwithstanding the taxonomic upheaval, there’s no question that Campephilus woodpeckers and Dryocopus woodpeckers are only distantly related, that their similarities are the product of convergent evolution, and that these similarities are far more superficial – involving size and coloration – than structural or behavioral. Formerly, some incorrect taxonomic assumptions led to the lumping of Campephilus and Dryocopus into the “tribe” Camphelini, an idea that’s discussed and dismissed in the first paper linked to above. This has been one factor in perpetuating some fairly common and persistent misconceptions – that the two species are closely related, that they occupy or occupied the same ecological niche and might be competitors, and that hybridization might be possible (something I hear surprisingly often).
The following differences are relevant to this discussion:
- Bill size and shape. These are dramatically divergent as any comparison shot of specimens makes clear. It’s also worth noting that the three North American Campephili are closely related to each other. DNA analysis suggests the three are distinct species and the Cuban ivorybill may be more closely related to the Imperial Woodpecker than the mainland US species. This study suggested that divergence among the three took place between .08 and 1.6 million years ago. The southern members of the genus are more remote cousins, having diverged approximately 3.9 million years ago. At one time, the southern species were considered a distinct genus, and they have smaller bills, both objectively and relative to body size. Magellanic Woodpeckers have the smallest bills relative to body size in the genus, and their foraging behavior is more Dryocopus-like than their congeners’.
- Neck length. The much longer neck of the ivorybill allows for a broader range of motion.
- Foot and leg structure. Campephilus woodpeckers have a unique variation on what have been called pamprodactylous feet. (Wikipedia and David Sibley both miss the vast difference between Campephilus foot structure and that of most other woodpeckers.) In this genus, the hallux (first) and fourth toe (the rear toes) are both on the outer edge of the foot; the toes can be rolled forward for climbing and backward for perching in a manner that looks more zygodactylous. (The preceding links to images of Sonny Boy, the juvenile ivorybill, and Kuhn are great illustrations.) The fourth toe is highly elongated, the longest toe on the foot, and the hallux, (in the ivorybill, the outermost toe) is relatively longer than in any climbing woodpecker species. The second and third (innermost toes) are angled inward. This is shown quite clearly in a number of the images from the Singer Tract, including Plate 13 in Tanner.
Detail of Tanner’s Plate 13 showing foot structure. Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library
- Dryocopus woodpecker feet are closer to being truly zygodactylous – two in front, two behind, with limited mobility and the hallux as the inner rear toe, although the fourth toe can be rolled outward to some extent; this provides less stability when making lateral blows.
Pileated Woodpecker foot showing zygodactylous structure and slight outward rotation of fourth toe. Photo courtesy of Carrie Griffis, who posted it on the Woodpeckers of the World Facebook group and kindly granted permission to include it here.
In addition, Campephilus woodpeckers typically climb and forage with their legs both farther apart and higher relative to their bodies than Dryocopus. This enables them to keep their lower bodies closer to the trunk and move their upper bodies more freely, providing more stability for making powerful, lateral blows.
4. Tail structure: the ivorybill’s tail feathers are long, thin, barb-like, and stiffer than the pileated’s. The tail serves as an anchor and also helps allow for a broader range of motion.
Middle Tail Feathers: Flicker, Ivory-billed, and Hairy Woodpecker
Pileated Woodpecker Tail Feathers. Note how the longest one resembles that of a Flicker more than that of an ivorybill.
5. There other structural differences, including wing shape, but these are the main ones that point to how Ivory-billed Woodpeckers have evolved in a way that makes bark scaling their most efficient foraging modality, whereas Pileateds are far better suited to digging, using a perpendicular motion.
Much of the foregoing is based on Walter Bock’s analysis of woodpecker adaptations for climbing, which was also discussed in depth here. I’ve tried to explain Bock’s key points in straightforward and less technical terms. A longer quote from Bock appears at the end of this post.*
In addition to these structural differences, Pileated Woodpeckers (and to the best of my knowledge all their congeners) regurgitate when feeding young. Campephilus woodpeckers carry food to the nest and appear to be highly dependent on beetle larvae when caring for their nestlings. This means that Pileated Woodpeckers have to ability to take advantage of multiple food sources during nesting season, while Ivory-bills have a more limited range of options. While I don’t think this supports Tanner’s theory of old-growth dependence, it does point to a higher degree of specialization that would impact numbers, range, and suitability of habitat.
At the same time, the anatomical differences and degree of specialization convince me that certain types of feeding sign are beyond the physical capacity of a Pileated Woodpecker and are likely diagnostic for Ivory-billed Woodpecker.
There is a dearth of clear images showing Ivory-billed Woodpecker feeding sign. There are a handful of photographs, most of them very poor. The majority were taken in the Singer Tract and some showing work on pines were taken in Florida by Allen and Kellogg. Few of them depict the high branch work that Tanner described as being characteristic, and when they do, there’s virtually nothing that can be discerned from them. It is also not entirely clear that Tanner’s attribution of feeding sign to ivorybills was always based on direct observation, which makes us wonder whether some of the work might actually have been done by squirrels. Regardless, this makes it difficult to draw inferences from the existing body of imagery.
That said and with awareness of the perils in extrapolating, one lesser known image from the Singer Tract is worth comparing with the work on boles that’s been discussed in multiple posts.
“The Blind at Elm Rock”, Ivory-billed Woodpecker nest tree and detail showing scaling and excavation on trunk. Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library
This is a view of the 1935 nest tree, which was a red maple. It’s taken at a different angle than the more familiar shots, so it shows some large areas of scaling on the bole that the others do not. While I can do no more than infer that this was done by ivorybills, it’s clearly old, and there’s an abundance of excavation in the underlying wood; nevertheless, the edges and contours of the scaling are strikingly similar to the work we’ve found on boles, especially the area at the lower right, just above the intervening foliage.
This is the jagged appearance I described in the previous post; the similarities are most evident in the picture below and on the home page. 
Because there are so few informative images of ivorybill feeding sign, the best available option is to look at the work of other Campephilus woodpeckers. Even though they are not as closely related as the Cuban ivorybill or the imperial, their morphology and foraging behaviors are similar; even the work of the smaller-billed but oft-photographed magellanic can provide some clues. I’ll examine this and some probable identifying features of squirrel scaling in the next post, which will take a close look at scaled patches on trees.
*”. . . in most woodpeckers, as, for example, the pileated woodpecker, the legs are held more or less beneath the body,the joints are doubled up,and the tarsus is held away from the tree trunk. This position of the legs is disadvantageous for the bird, because the body is held away from the tree trunk and the muscles of the leg are working at a mechanical disadvantage; the analogy is to the mountain climber who is standing on a narrow ledge with hand holds only beneath his chest. In the ivory-billed woodpecker, the legs are directed away from the center of the body, and the tarsus is pressed against the tree trunk. This method allows the body to be held close to the tree, with the joints of the leg extended. Hence the leg muscles have a mechanical advantage, because they are at the beginning of their contraction cycle and are acting along the length of the segments of the leg. When the body is held close to the trunk, it not only decreases the outward component of gravity but allows the tail feathers to be applied to the supporting surface for a greater distance from their tips. If the bird is climbing on smaller limbs, the feet can encircle the limb and thus obtain better support. However, no matter what size the limb is, the disposition of the legs and the spreading of the toes of the ivory-billed woodpecker furnish direct and powerful resistance to both the lateral and backward motions of the woodpecker when it is at work and, with the tail, furnish a tripodal base of great strength against the pull of gravity.”
Not So ‘Virgin’ Forest: The Singer Tract Myth Debunked
Posted: December 18, 2015 Filed under: Habitat, Ivory-bill History, Old Growth, Uncategorized | Tags: Frisby plantation, habitat, Ivory-billed Woodpecker, James T. Tanner, madison parish, old growth, Richard Pough, Singer Tract, specialization, T. Gilbert Pearson, Tensas River, theodore roosevelt, virgin forest 3 CommentsUpdate: This post includes hard data about the extent of old growth in the Singer Tract (scroll down past all photographs) and in ivorybill home ranges. The general points made below remain valid, although some of the wording is perhaps too strong; Tanner overestimated the amount of old growth in the Tract ( at “over 80%” v. 72% in fact), and the Mack’s Bayou home range was predominantly second growth.
This post is a companion to the previous one and to others discussing habitat conditions in the Singer Tract. Those posts reference Richard Pough’s 1944 report to the Audubon Society. Pough, whose study was never published, noted that much of the Singer Tract had actually been under cultivation prior to the Civil War. But it’s worth taking a closer look at just how much.
Tanner characterized the Singer Tract as “the largest tract of virgin timber in the Mississippi Delta,” contending that it contained “120 square miles of virgin forest in 1934”. He also wrote that the largest plantation “had about 3000 acres under cultivation,” while suggesting that “some of the early settlers along the Tensas River cleared land along the river banks for cotton fields.” Thus, the myth of the Singer Tract as virgin forest was born.
It’s not clear where Tanner got his information, but some of his characterizations are not supported by the historical record; the language about “early settlers” almost seems disingenuous when one looks at the history of Madison Parish. (Rootsweb has many pages devoted to this subject, and I’ve drawn heavily on them for this analysis.) As should become evident, there was a great deal of human activity in and around the Singer Tract, especially prior to the Civil War. I will suggest that most, perhaps virtually all, of the arable land in the parish, had been cleared for agricultural purposes and that the Singer Tract was a mix of second growth and remnant old growth, most of which was in the lower-lying, wetter areas that Tanner deemed to be less suitable for ivorybills.
A 1937 Masters thesis in economics by Robert L. Moncrief, “The Economic Development of the Tallulah Territory”, provides a great deal of information about the parish and its history. In the post-Columbian era, the area was very sparsely settled until the 1830s. Madison Parish was established in 1839, and in 1840, steamboats began plying the Tensas River. A major population influx began in 1836, and the population kept growing until the Civil War, going from 5,142 in 1840 to 14,133 in 1860. The war led to a dramatic decline to a mere 8,600 in 1870. Over the next couple of decades, the numbers grew again to 14,135 in 1890. Changing economic conditions and the boll weevil outbreak caused another decline that was only reversed between 1920 and 1940, when the number of residents reached 14,826. By 2010, it had fallen to 12,093.
Cotton and the quality of the soil drove this influx. By 1850, there were 27 landowners in the parish who owned more than $20,000 (over $590,000 in 2015 dollars) worth of real estate. The largest holding was valued at $140,000 (well over $4,000,000 in today’s dollars).
According to Moncrief, “the newcomers cleared away the heavy forests and planted the new ground in the favored crop then, as now –– cotton. They cleared all the lands fronting water courses (which are the highest and most desirable lands for cultivation in this region) to form a continuous line of plantations along the streams.” Streams in this context refers not just to the Tensas but also to the smaller non-navigable bayous. Cotton raised along the smaller streams was brought down to the Tensas in flat-bottomed boats.
Moncrief’s thesis also includes figures for cotton and corn production in Madison Parish. Cotton production peaked at over 46,000 bales in 1858. (Pough was apparently incorrect in stating it was over 100,000 bales; he may have combined the total with that of an adjoining parish.) It had fallen to 1,830 by the end of the war. Production recovered between 1870 and 1875 and reached a postwar/pre-boll weevil peak of 25,981 bales in 1890, about the same level of production as in 1936. Corn production peaked at 618,620 bushels in 1859, falling dramatically after the war, peaking at 836,000 bushels in 1909, and then falling to 320,000 by 1936. My crude, back of the envelope estimate based on yields of 5 bales per acre for cotton and 15 bushels per acre for corn, suggests that between a quarter and a third of the total acreage in the Parish was under commercial cultivation prior to the war.
While Moncrief’s paper evokes Tanner by describing the Singer Tract as 81,102 acres (126 square miles) of virgin timber, it also notes, “The tract includes several abandoned and grown up plantations, which after the Civil War, reverted to the state and were later sold to the present owners.” The ruins of one plantation house are still standing, deep within the Tensas National Wildlife Refuge.
While it was adjacent to and not strictly part of the Singer Tract, the story of the Frisby Plantation is illustrative. The plantation was established in the early 1850s with land acquisitions taking place over the next decade. Norman Frisby, the founder, was murdered by his nephew by marriage in an 1863 in a dispute over property. When Frisby’s widow was forced to sell the plantation in 1870, it totaled 19,479 acres, and its crops generated over $77,000 in revenue (the equivalent of $1.36 million in 2015). Tanner visited the site of the plantation and photographed one of its old fields. I haven’t been able to pinpoint the location of the old house; one 19th century survey survey seems to place it in Tensas Parish, near Fool’s River. Another account (from the history of the Sharkey Plantation discussed below) says it borders Disharoon (or Dishroom) Bend, much closer to the core of the Singer Tract. As shown on this overlay of 1875 land ownership on a modern map, the Frisby holdings included parcels adjacent to Mack’s Bayou and on Dishroom Bend.
The maps help flesh out the story. An earlier and incomplete parish-wide map of patentees shows that many parcels in the Singer Tract were purchased well before Frisby started acquiring land in the 1850s. Lands purchased in the 1840s include parcels along John’s and Mack’s Bayous, which makes sense since frontlands along streams were most desirable. This history of the Sharkey Plantation reveals that land sales began in the heart of Tanner’s search area during the 1840s. The author explains that the Sharkey plantation and others like it were more like communities, with a cluster of families (and presumably their slaves) living in close proximity, near a watercourse. The 1875 map shows that much of the Singer Tract remained in private hands even after many parcels were abandoned during the Civil War.
Perhaps even more telling is this hand drawn map of Madison and Carroll Parishes from 1862. It shows the locations of towns, roads, ferry crossings, and plantations in the Singer Tract area. While it is incomplete and John’s Bayou is not shown, Sharkey Road is there, cutting in a southwesterly direction from the Richmond-Carthage road, crossing Alligator Bayou, and the Swearingen parcel. Another road crosses the heart of the Mack’s Bayou home range and the Tensas itself. The map delineates abandoned plantations and appears to show that, except for those abandoned areas, some cotton was being grown in every division of the Singer Tract. However limited the agricultural activity may have been in these sectors, the area was hardly a primeval wilderness; habitat had been fragmented; and old growth conditions were likely restricted for the most part to areas unsuitable for farming.
This passage from an 1885 article from the New Orleans Times-Picayune sheds some additional light on conditions in the area both before and after the Civil War. “But little has been said about Tensas River and Joe’s Bayou as, but little interest is there as compared with former years. Before the war there was a continuous planting interest all along those two streams but overflows and the war left them to grow up into weeds and bushes. In 1870 Mason, and later Loyd bought cattle from other parts of the country and carried them to those bayou places for pasturage, wherein a few years they made large sums of money. This was in the neighborhood of Quebec, which before the war was a flourishing little city, shipping 7090 bales of cotton. It was at the junction of the Tensas River and the railroad. It is now a waste place and to pass there on the railroad you would never know that a town had been there.” (In The Race to Save the Lord God Bird, p.76 Hoose plays into the virgin forest myth by claiming that railroads “finally reached the Tensas River sometime around 1900.”) Quebec was just a few miles outside the tract, near Bayou Despair, where Tanner listed a pair from 1934-1936.
The Rootsweb pages provide a couple of additional and important pieces of information.
Theodore Roosevelt visited Madison Parish in 1907. Roosevelt’s descriptions provide added detail about conditions in and around the Singer Tract several decades after the Civil War. According to Roosevelt:
“Beyond the end of cultivation towers the great forest. Wherever the water stands in pools, and by the edges of the lakes and bayous, the giant cypress loom aloft, rivalled in size by some of the red gums and white oaks. In stature, in towering majesty, they are unsurpassed by any trees of our eastern forests; lordlier kings of the green-leaved world are not to be found until we reach the sequoias and redwoods of the Sierras. Among them grow many other trees–hackberry, thorn, honeylocust, tupelo, pecan, and ash. In the cypress sloughs the singular knees of the trees stand two or three feet above the black ooze. Palmettos grow thickly in places. The canebrakes stretch along the slight rises of ground, often extending for miles, forming one of the most striking and interesting features of the country. They choke out other growths, the feathery, graceful canes standing in ranks, tall, slender, serried, each but a few inches from his brother, and springing to a height of fifteen or twenty feet. They look like bamboos; they are well-nigh impenetrable to a man on horseback; even on foot they make difficult walking unless free use is made of the heavy bush-knife. It is impossible to see through them for more than fifteen or twenty paces, and often for not half that distance. Bears make their lairs in them, and they are the refuge for hunted things. Outside of them, in the swamp, bushes of many kinds grow thick among the tall trees, and vines and creepers climb the trunks and hang in trailing festoons from the branches. Here, likewise, the bush-knife is in constant play, as the skilled horsemen thread their way, often at a gallop, in and out among the great tree trunks, and through the dense, tangled, thorny undergrowth.”
The most salient point here is that Roosevelt’s “great forest” applied to low-lying areas in which there was standing water (something that Hoose glosses over). Roosevelt also saw three Ivory-billed Woodpeckers:
“The most notable birds and those which most interested me were the great ivory-billed woodpeckers. Of these I saw three, all of them in groves of giant cypress; their brilliant white bills contrasted finely with the black of their general plumage. They were noisy but wary, and they seemed to me to set off the wildness of the swamp as much as any of the beasts of the chase.”
A photograph from the hunt is here. Tanner seems to have been unaware of the Roosevelt encounter. Roosevelt’s visit came just 17 years into cotton farming’s second decline and 52 years after the end of the Civil War. Habitat conditions are likely to have been poorer in general than when Tanner was there 3 decades later. The relative ease with which Roosevelt saw three ivorybills (despite their wariness) suggests they were not uncommon in 1907 and calls Tanner’s assumptions (pp. 48-50) about fire, tree death, and population influxes between 1911 and 1930 into question.
There’s another gem in the Rootsweb pages. It’s not directly on topic, but it relates to Tanner’s later dogmatism. In arguing for extinction and dismissing post-Singer Tract reports, many of which involved birds being flushed from tree stumps or other locations near the ground, Tanner characterized this behavior as being characteristic of pileateds not ivorybills.
Rootsweb has a newspaper account of T. Gilbert Pearson‘s visit to the Singer Tract in 1932. Pearson (who was President of the Audubon Society at the time) was the first ornithologist to confirm the presence of ivorybills in the Tract. He saw, “The birds . . . feeding on stumps of rotting trees, the tops of which had been broken off. A favorite place for feeding is also on dead limbs at or near the tops of the very tall sweet gum trees found abundantly in this region.”
The evidence that relates directly to Tanner’s study area and its immediate environs suggests that claims about “virgin forest” and IBWO dependency on old-growth are based on flawed premises. The Singer Tract was no doubt a remarkable place, a huge area of contiguous and relatively undisturbed forest, but it’s clear that much of it was not old growth or “virgin”.
It’s more useful to think about what the Singer Tract is likely to have offered Ivory-billed Woodpeckers – some measure of seclusion, enough big trees for roosting and nesting, and an abundance of standing and fallen deadwood. The myth that the Ivory-billed Woodpecker required vast tracts of “virgin” forest may be emotionally compelling, but it’s not based on evidence; it’s time to put it to rest.
I’m looking forward to spending a week in the field starting just after Christmas.
Some Thoughts on The Ivorybill’s Decline And A Change of Plans
Posted: May 30, 2015 Filed under: Ivory-bill History, Old Growth | Tags: adaptation, Cuban Ivory-billed Woodpecker, James T. Tanner, old growth, Pileated Woodpecker, search area, Swamp 7 CommentsJamie Hill, who has worked with the Cornell and Auburn teams, recently posted a Facebook link to a very interesting article from the September 2014 issue of Smithsonian. Ivory-billed Woodpecker aside, the piece is well worth reading, but for the purposes of this blog, the article got me thinking about reasons for the ivorybill’s decline and the possible role of the longleaf pine. These ideas are not entirely new or original with me; Lester Short went even further, suggesting that pine might have been the ivorybill’s primary habitat; Jerome Jackson devoted several pages of In Search of the Ivory-billed Woodpecker to pines, and Fangsheath of the ivorybill researchers forum has hinted at this too.
I was struck by just how congruent the historic range of the ivorybill is with the range of the longleaf pine (Pinus pilastrus). The overlap is not exact, and the pre-Columbian range of the ivorybill extended as far north as Ohio. Nonetheless, conditions in the Singer Tract were objectively quite different from what they were in many other parts of the historic range.
A recent blog post on the Tallahassee Democrat site reiterates the conventional wisdom about the species and the reasons for its decline. Author Budd Titlow writes: “Before the Civil War, when much of the southeastern U.S. was covered with vast tracts of primeval hardwood swampland, ivory-billed woodpeckers ranged from North Carolina south to Florida, west to Arkansas and Texas, and north into Oklahoma and Missouri. Then, after the Civil War, extensive logging of these old-growth swamps wiped out most of the ivory-billed’s habitat in one fell swoop.”
While there’s some truth to this history, it’s also a stereotype that’s based in large part on an imperfect reading of Tanner’s monograph and even more on Tanner’s dedication to protecting the Tract as the last remaining extensive old-growth stand in the southeast (although the Tract contained considerably less old growth than Tanner believed). Tanner’s efforts were admirable; the loss of countless acres of magnificent old-growth swamp forest was devastating environmentally and is unquestionably something to be mourned, but it seems unlikely that the destruction of these forests was the primary cause for the ivorybill’s decline.
The species was known to be disappearing by 1890 or even earlier, and Chester Reed’s 1906 Bird Guide to Land Birds East of the Rockies stated that the birds were restricted to isolated parts of Florida and possibly to “Indian Country” (Oklahoma). In The Travails of Two Woodpeckers, Noel Snyder, who attributes the decline primarily to hunting, points out that intensive logging of bottomland hardwoods began between 1890 and 1900. Logging of pine forests began considerably earlier, and these forests were severely fragmented, even before the Civil War. Snyder reads the early record (I think selectively) as indicating that ivorybills strongly preferred bottomland hardwoods and seldom used pines, in contrast to the Cuban ivorybill and the Imperial.
Jackson takes a different view, citing multiple references to the use of pines for feeding and nesting. Where Snyder reads Alexander Wilson’s early account as reflecting a preference for “swamps and bottomlands”, Jackson reads him as describing the preferred Carolina habitat as “a mosaic of baldcypress swamp and pine uplands, similar to the habitat in Florida”. Jackson goes on to suggest that, “It appears . . . that ivory-billed woodpeckers will inhabit both hardwood forests of river bottoms and pine forests of higher elevations, particularly old growth forests supporting healthy populations of beetles. They seemed to do best at the interface of these forest types, taking advantage of the resources of each.” (Emphasis added).
This meshes well with what Allen and Kellogg observed in Florida in 1924; the birds nested and roosted in cypress and were observed and photographed foraging in open pine forest. The Lambs’ limited observations in Cuba suggest something similar, a preference for roosting in pines but an equal division between pines and hardwoods for foraging.
Thus, it seems possible that the Singer Tract was actually suboptimal habitat for the ivorybill, since it contained no pine and little cypress. I’m also led to suspect that habitat fragmentation, rather than habitat loss may have been central to the decline of the ivorybill, with hunting as one of several other contributing factors. This fragmentation actually began well before the Civil War, but it accelerated with the post-war destruction of the longleaf pine forests, followed by the logging of the bottomlands. I’m personally convinced that the species beat the odds and survived, using one or both of the strategies discussed in this post. I wonder whether some of the modern search efforts have focused excessively on the bottomland hardwood model and not enough on areas where there’s an interface between forest types.
On a different note, I had planned to make my final trip to our search area for the season during this week and next. Water levels are very high right now, so I’ve decided to postpone until late July. Better to endure the heat and humidity than to be unable to move around in the woods.
