Historic Range Hypothesis: A Bits ‘n’ Pieces Epilogue

In retrospect, I realize that I could have stated my hypothesis about historic range more explicitly in the Bits ‘n’ Pieces series, here, here, here, here, here, and here. My treatment of this subject draws on and expands upon Tanner, Jerome Jackson’s extensive review of the historical record, the work of Benjamin Leese, and Appendix E in the U.S. Fish and Wildlife Service’s Ivory-billed Woodpecker Recovery Plan, supplemented by my own research and review of the source material.

I got somewhat too focused on specimen records and even more so on habitat types. The version of the map I created for the series reflects that focus, by including barrier islands, for example. The subjects of range and habit are of course intertwined, but I’ll state the hypothesis with respect to range upfront and follow it with a more detailed discussion:

The Ivory-billed Woodpecker’s range was considerably more extensive and than is recognized by the general public and than has been represented in much of the literature, both popular and scientific. All published range maps of which I’m aware, including Hasbrouck’s (1891), Tanner’s (1942), Jackson’s revised and redrawn version of Tanner (2004), and online, poorly reflect the historic range, especially east of the Mississippi.

This has implications in terms of habitat requirements and adaptability as well.

I suggest that the northern limit of the ivorybill’s range was just above 40 degrees North and that the western limit was approximately 98 degrees West. There are no archaeological or other records from over 2000′, so I’d exclude higher elevations in the Appalachians and Ozarks. I think the previous maps are accurate to the extent that they show the range as extending farther west in the Red and Arkansas River basins than in the Missouri.

To express it somewhat differently, I think ivorybills could be found as far north as the lower Delaware River on the Eastern Seaboard and that they could be found in riparian corridors into the lower reaches of the Appalachians from there south.

In Florida, I think it’s conceivable that the range extended to the Upper Keys. In the southwest, I’d draw the line near Port Lavaca, Texas to west of Tulsa, Oklahoma. Except for an archaeological find in northeastern Nebraska that almost certainly involved trade items, the northernmost specimen record from west of the Mississippi is from Forest Park, MO (more on that below).

The story seems to have been somewhat different in the Ohio River watershed, where both archaeological evidence and sight records suggest that birds were present far upstream from the Mississippi confluence and along tributaries well north of the river itself.

I’ve created another map showing both the limits of my hypothesized range and selected reports from what could be considered the edges of that range. A screen cap is below. Click on this link for annotations. Although some of the records are pre-Columbian (the earliest estimated as dating to 0-200 CE/AD), I suspect this was the approximate range until the mid to late-18th century.

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Hypothesized limits of Ivory-billed Woodpecker range and selected records from areas outside those shown on most other maps.

Thus my hypothesized range is considerably more extensive than the conventional one (shown immediately below). On the Eastern Seaboard, it extends much farther north and also farther inland. It is far greater within the Mississippi watershed, extending to north of Columbus, Ohio, and encompassing all but the higher elevations in the Appalachians (based on the archaeological site at 2000′ near Lebanon, VA), reaching farther north and west in Arkansas and Missouri.

It was also somewhat more extensive in Texas and Oklahoma, reaching farther into the plains and a little farther south than the maps suggest. Outside of coastal areas, the presence was probably limited to riparian corridors, with those in the western part of the range (at least) being narrow.

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Map derived from Jackson’s revision of Tanner’s 1942 publication. Similar maps are widely reproduced.

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Hasbrouck’s Ivory-billed Woodpecker Range Map (1890). Shaded areas reflect what Hasbrouck believed to be the range at the time of writing.

While what I’m suggesting may seem heretical to some, it’s well-supported by the archaeological record, accounts from early explorers and naturalists, and collection records or reports thereof, albeit to a lesser extent. I covered many of the records that led to my formulating this hypothesis in previous posts; I won’t recapitulate all of them here, but one passage is worth revisiting. Two notes on technical terminology: middens are most easily defined as “dumps for old domestic waste“, and tarsometatarsi are the lower leg bones found in birds (and some dinosuar fossils).

If our knowledge of the Ivory-billed Woodpecker were based on the archaeological record alone, we’d think of it as an upland species. Further, we might very well assume that it ranged from the hills of Georgia, to the Alleghenies in Virginia, to central Ohio and west-central Illinois. 

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

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

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

In an unpublished 1989 update to his monograph (housed in the archives at Cornell), Tanner accepted additional reports, including archaeological finds from Scioto County, Ohio (15th or 16th-century) and Madison County, Illinois (Cahokia Mounds, approximately 15th-century), as well as a collection record from Forest Park, Missouri and an 18th century record from Lincoln County, Kentucky. Since that time, additional archaeological records from Georgia, Virginia, West Virginia, and Ohio have turned up.

Thus, the case for ivorybill presence both in the lower reaches of the Appalachians and well up the Ohio River (and its tributaries) is compelling, and any suggestion that items found in Native American middens might be trade goods is pure speculation with no evidence to support it.

In a paper titled, “Putative Records of the Ivory Billed Woodpecker in Pennsylvania and the Mid-Atlantic” (2016 Pennsylvania Birds, 20(2):71-72), Leese suggested that eastern Pennsylvania and Southern New Jersey might be the northern limit on the Atlantic Coast. I agree and might even go a step further and argue that the available evidence strongly supports that view. The discussion below relies heavily on material Leese discovered, though I disagree with Leese’s conclusion that a more extensive range and more varied habitats support Snyder’s argument that hunting was the “main cause of the species’ extinction”.

This idea that ivorybills ranged so far north on the East Coast will probably be the hardest for many to swallow. Bear in mind, however, that Audubon described the ivorybill as an accidental in Maryland. Audubon’s discussion of range is odd; he didn’t mention Florida, and there’s nothing to support the idea that the western part of the range extended to the foothills of the Rockies. But he would have been far better informed about the Eastern Seaboard.

In any event, his description dates to the 1820s, by which time the range was likely shrinking. As discussed previously in the series, I suspect that the extirpation of the beaver played a major role in the ivorybill’s decline outside of Florida. Beavers were probably extirpated in New Jersey by 1820 (Van Gelder 1984). It’s reasonable to infer a similar date for eastern Pennsylvania.

To expand on this beyond the previous posts in the series, Peter Kalm, a prominent European naturalist and student of Linnaeus, listed the ivorybill as present in the Delaware Valley and distinguished it from the Pileated, which he described as “a Black Woodpecker with a red head” and “frequent in the Pennsylvanian forests”.

It’s not clear whether Tanner was aware of Kalm’s 1749 record, which was described in The Auk in 1903. The author of that paper suggested that this record should be taken “cum grano salis,” primarily because there have been no other records from the state. Or have there?

While it is ambiguous, Leese discovered a letter from Alexander Wilson, written during the early years of his career, when he was living on William Bartram’s property near Philadelphia; it is strongly suggestive of ivorybill, describing a large and “most extraordinary Blackheaded Woodpecker”. This was at a time when Wilson seemed to be in the process of learning his birds, and he did not mention it in later correspondence, which leaves room for doubt.

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While Wilson’s description is not very detailed, I find it suggestive. And as noted previously, I think the only basis for rejecting Kalm’s account (and he seems to have otherwise been meticulous) is what we think we know about the ivorybill, a knowledge base derived from observations dating to between 60 and 190 years later. While there’s no way to prove it, I think Kalm’s listing should be treated as credible; it would be if a more common species were involved. Leese mentioned a couple of additional 18th century reports from Pennsylvania (included on the map) but found them questionable.

I’m not aware of anyone else having made this observation, but I think it’s a very important one. In the 1740s, the ivorybill had not yet acquired the mystique that would accompany it from the mid-1800s to the present, a mystique that was popularized if not invented by Audubon. This lends greater credibility to earlier reports such as Kalm’s. I think the same principle supports Jefferson’s listing of the ivorybill as resident in Virginia (which may have been based on his own observations) a couple of decades after Kalm and a few decades before Audubon.

To return briefly to Wilson and another report from an unexpected location, Jackson (2004) references a specimen collected by Wilson from somewhere between Winchester, Virginia and Martinsburg in what is now West Virginia (presumably in the Potomac watershed). I have not located the primary source for this reference, which may be in the archives of the Philadelphia Academy of Natural Sciences, but here’s Jackson’s:

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The Putnam County, WV find is also interesting, as it suggests a bird that may have been collected for trade rather than being acquired through it.

I want to touch briefly on two additional records, both involving specimens. The facts related to these records point to how even specimen evidence is not free from ambiguity. For one thing, specimen tags often reflect shipment rather than collection locations. In addition, labels could have been changed and replaced at any point in the chain of custody between hunter and museum.

The first specimen is housed at Cornell (and I have seen it myself). It was collected in 1898 from the “Florida keys”. In Appendix E of the Ivory-billed Woodpecker Recovery Plan, it is suggested that this might actually refer to one of the forested “keys” in the Everglades rather than to one of the offshore islands. However, given the ivorybill’s use of barrier islands on the Atlantic Coast and the 10,000 Islands in Florida, it does not seem farfetched that the specimen could have been collected somewhere in the Upper Keys proper.

From my current perspective, based on the Recovery Plan’s information about habitat on the southwest Florida coast, both possibilities seem plausible and neither is particularly surprising. However, neither location would ever have had many characteristics in common with stereotypical ivorybill habitat –  vast, contiguous bottomland hardwood forests. (Although he sometimes seemed to embrace this stereotype later in life, Tanner recognized that ivorybills lived in varied habitats, as have others who have studied the subject in depth.)

The other specimen, labeled  as being from Forest Park, Saint Louis, Missouri, escaped Tanner’s notice initially but was included in his 1989 update. It is housed at the Colorado Museum of Natural History in Denver and was collected in 1886. Matt Courtman pointed out that by 1886, Forest Park was hardly an isolated spot; it attracted “hundreds of thousands” of visitors a year,was located on the outskirts of a city with a population of 400,000, had been at least partially landscaped, and was accessible by streetcar.

So not only did this collection come from well north of what’s commonly accepted as the historic range; it may have come from a managed parkland on the outskirts of a major city, hardly stereotypical ivorybill habitat. The location and date are surprising, so it’s possible that the specimen was collected somewhere else (though not in a different region) and that Forest Park was the shipping location.

This may be so, but an 1886 collection from anywhere near Saint Louis is a paradigm-buster, regardless of the exact location, as this 1884 map suggests. Forest Park, to the southeast of Florisant and Ferguson, which are indicated by the red circle on the map, is not shown.

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Detail from 1884 map of Missouri, showing Saint Louis and environs. Note both the network of railroad lines and the apparent population density.

Tanner’s original map showed the ivorybill as never having ranged farther north than the Missouri bootheel (the southeastern corner of the state) and as having been extirpated from all but the southernmost tip of that region by 1880. The last specimen collected in Missouri dates to 1895, from just north of the bootheel “eight miles southwest of Morley.” (Widdman, 1908). Tanner seems to have been unaware of this record, which is mentioned in Jackson, who could not locate the specimen itself.

Tanner received at least one report (1937) from Dallas County, Missouri, which is northwest of Springfield, in the upper (southern) reaches of the Missouri River basin and well outside the generally accepted historic range. The source was a local Audubon Society officer, and the letter is archived at Cornell. There appears to have been no follow-up. According to the Recovery Plan, reports from this general area continued until 1949.

Though his map of the range ca. 1890 suggests a northernmost limit in Mississippi and Louisiana, Hasbrouck (citing Cooke, Bird Migration in the Mississippi Valley) mentioned 1884 records from near Kansas City and undated claims of former breeding near Fayette, along the river in central Missouri; Tanner considered these questionable or accidental. I agree that they’re somewhat questionable but not that they could have been accidental, since both purportedly involved breeding.

Reading Cooke reveals that both were second-hand accounts. The Kansas City report includes no details except that birds were observed “during the past few winters”, and “it probably still breeds in that vicinity”. For Fayette, the source was identified as a local farmer and egg collector by the name of Lientz, but the former breeding claim is devoid of any details, including the informant’s name.

Thus, the possibility of mistake or miscommunication exists in both instances, as in the seemingly credible report from eastern Nebraska discussed in Part 2; however, Jackson also references Harris’s Birds of the Kansas City Region (1919), which lists a “Judge Guinot” and others” for the Kansas City area records, in the “deep woods of the Missouri bottoms”. No date is given, but it seems possible if not likely that Guinot (1855-1935) was Cooke’s source

While I think the historic range probably extended as far as Kansas City, the case seems a little weaker to me than it does for the eastern seaboard and Ohio Valley –  given the paucity or absence of archaeological evidence or early reports from the Missouri River watershed, a key route for explorers, traders, and early settlers. For example, Featherstonhaugh, who crossed the Missouri River basin near the confluence with the Mississippi in the 1830s, described the northern limit as being considerably farther south, in the Arkansas-White River watershed. But perhaps there’s more to uncover about the ivorybill’s history along the Missouri.

As with anything ivorybill related, it’s probably best to be comfortable with not knowing and even to revel in the uncertainty.


Trail Cam Captures Redux: Beyond (My) Reasonable Doubt, Part 2

The previous post generated a number of responses, mostly positive, but there were a couple of negative remarks, one of which I thought I should address.

One claim was that this new way of examining the imagery (which was misleadingly described as “enhancement”) confuses the issue and makes the images harder to assess. In reality, the processes used in the previous post and in this one are for the most part not “enhancements.” While I have used various image enhancement tools in the past, most of these treatments use unaltered original images to create composites that make it possible to separate figure from ground and parts of the target from artifacts. It’s not a perfect method, but it’s an illuminating one, even with low resolution images. It requires no special forensic expertise. As should become clear from this post, it can also be useful for estimating size.

The images examined in this post were all captured December 7, 2014 on a Reconyx Trail cam that was showing its age. They were previously discussed here, here, and here.  As in the previous post, I’ve used Luminar to create the composites and apply various effects for this deeper dive. As always, views can be had by clicking on the images themselves; mousing over the images will reveal captions in most instances, and I have added versions with arrows to help orient you. I strongly encourage you to examine the images closely.

One initial comment about these images and the ones discussed in the last post: I’m personally convinced beyond a reasonable doubt that two of those images show Ivory-billed Woodpeckers. The images discussed in this post show fewer details, so they may not be quite as compelling. Either way, the captures under discussion are only part of the mosaic, and the subjective conviction that we have found Ivory-billed Woodpeckers in two locations is not solely dependent on them. The audio from last year, for example, is strong evidence in its own right. Go here for a detailed discussion of evidence gathered since 2009

I’ve reposted the original captures in tiled mosaic form below; I’ll follow that with some composites and comparisons among the images. I think the results are helpful if not quite as revelatory as the ones in the last round.  A very prominent American birder tweeted that one of the images below shows a Blue Jay (9.8-11.8″) and characterized the suggestion that it might be an ivorybill as “crazy”. (This is the capture I think is likeliest for ivorybill in this group.) I think his knee-jerk suggestion is absurd, as this approach to reviewing the images should make more apparent.


I’ll begin with the raw image I’ve always liked most for ivorybill, as previously discussed in detail and in comparison with Imperial Woodpecker captures. (Note that the version comparing putative IBWO and IMWO has been enhanced.)


Suspected Ivory-billed Woodpecker


Rotated, resized image of Imperial Woodpecker in flight. The bird is angled downward and slightly away from the camera obscuring the bill and foreshortening the profile. An automated motion blur reduction feature has been applied to the image of the putative ivorybill.

The next image shows the difference between the foregoing frame and one captured approximately 40 minutes later. The bird to the left of the snag is clearly closer to the camera (which was approximately 85′ from the target snag), between it and the snag. The composite strengthens the impression that the suspected ivorybill is behind the tree and the foliage behind it, since at least some leaves appear to be between bird and camera. Frank estimated the foliage as being 15′ more distant.


In the earlier discussion, several Pileated Woodpecker captures, including the one below, were used for comparison. These captures were taken from a slightly different position, but that’s irrelevant to the issue of size relative to the reference object, the jug handle-shaped stub.


Pileated Woodpecker on Snag

It may be even more instructive to contrast the capture with the Red-headed Woodpecker, apparently caught as it was preparing to land on the snag. The comparison suggests that the two birds are approximately the same distance from the camera. The possible ivorybill’s body is considerably longer than the Red-headed Woodpecker’s wingspan (14-17″). Thus, between the Pileated Woodpecker (~16-19″, with southern birds typically on the smaller side) and the Red-headed Woodpecker, it can be inferred that the suspected ivorybill is approximately the right size (19-21″), considerably larger than a Red-headed and somewhat larger than a Pileated. I am unable to think of an alternative ID for a bird of similar size and shape, even leaving aside the fact that a white trailing edge seems to be present even in the original, unmodified version of the capture. (The trailing edge becomes more apparent when the image is processed to reduce motion blur.)


A different but related method of image processing is helpful for understanding the position of the bird relative to the snag and also suggests that another capture in the series is at least size-appropriate for ivorybill; the tuck and the long, pointed shape of the wings are also intriguing. The first composite shows the unknown bird and the Red-headed Woodpecker. (Note what seems to be a wing, species unknowable, protruding from behind the snag; it appears in the Red-headed frame and no others and had gone unnoticed until now. On looking again, this could also be a squirrel’s tail, albeit unusually positioned.) The second is an overlay of the suspected ivorybill capture and the unknown bird processed using Luminar’s “Color Burn” feature; the two birds appear to be approximately the same size and in the same plane. I’ve added a shot of a Pileated Woodpecker in flight, with wings in a similar position, for comparison.







Another capture from the morning of December 7 has always interested us. The underwing pattern and shape are suggestive of ivorybill and reminiscent of one of the Singer Tract photographs. But questions about size have lingered. Comparing this image with two others from the same deployment that show Red-headed Woodpeckers may be helpful, and it has pushed me toward favoring Ivory-billed Woodpecker for this capture as well.


Either Ivory-billed or Red-headed Woodpecker Depending on Size





This capture seems more ambiguous to me, but a few factors are more consistent with Ivory-billed Woodpecker than Red-headed Woodpecker. Both Red-headed Woodpeckers, one captured on the same morning under similar lighting conditions, appear to be closer to the camera than the possible ivorybill. My efforts at measuring wingspan were crude, but the suspected ivorybill seems to have a slightly greater wingspan, despite the upturned angle of the wings and apparent greater distance from the camera. This would tend to exclude Red-headed.

The comparison is also useful insofar as it shows that the wing and body shape of the possible ivorybill are not similar to the Red-headed Woodpeckers captured during this deployment. While Red-headed wing and body shapes can resemble ivorybill at certain angles and under certain lighting conditions, as Bill Pulliam documented years ago, the tail in this image looks too long relative to the body, and the wings look very narrow, at an angle that I don’t think would create an illusion of elongation.

As always, I’m open to correction, and my interpretations are provisional. Intelligent and informed comments are welcome.