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

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

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

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

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

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

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

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

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

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

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

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

Screen Shot 2017-12-22 at 2.40.00 PM

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

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.

Screen Shot 2017-12-22 at 3.42.31 PM

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.

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One Comment on “Bits and Pieces Part 5: More on Range and Habitat Variety”

  1. Compelling, thorough work, as always Mark. Among many useful insights, I found Bill Pulliam’s catch regarding the pessimism as to the future of the PIWO to be particularly illuminating—and entertaining. Also, I enjoyed your point about that if Ivorybills had gone extinct prior to 1700 we would have lamented the passing of that magnificent denizen of America’s UPLAND forests, the Ivory-billed Woodpecker!!!


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