Scaling Data 2012-2016

To expand on some of the data included toward the end of the March trip report (which is worth reading in in conjunction with this post), I thought it would be informative to provide a season by season and sector by sector breakdown of the scaling I and others involved with Project Coyote have found since the spring of 2012. To do so, I’ve gone through my notes and photographs and have done my best to reconstruct the data collected. While not complete (I’m quite sure a good deal more scaling was found in Sector 3 during 2013-2014, for example), I think this breakdown is a fairly accurate reflection of what we’ve found over the years.

As discussed in previous posts, I think extensive scaling on hickory boles is the most compelling for Ivory-billed Woodpecker. Bark on this species is thick, dense, and usually remains very tight for a long time. Extensive scaling on sweet gum boles and oaks (upper boles and large branches) is second among work that I’ve found. Work on small boles, and higher and smaller branches is somewhat less compelling and is more significant for its abundance. Some of the high branch scaling and work on smaller boled sweet gums may well have been done by Pileated Woodpeckers (and possibly by Hairy Woodpeckers), but the abundance, the presence of large bark chips in many cases, the way it appears in clusters, and the fact that Pileateds scale infrequently suggest a different source for much of it.

I have excluded all work where squirrels are suspected but have counted one tree, a hickory found this year, on which the work could well have been that of a Hairy Woodpecker. Hairies do forage for Cerambycid beetles just under the bark, but they’re only capable of removing tight bark in small pieces; their work on hickories is perhaps more accurately described as excavation through the bark.

The trail cam images toward the end of this post are the best we have (out of many thousands of hours of coverage) showing how these species forage on suspected ivorybill feeding trees.

All trees were live or recently dead (twigs and sometimes leaves attached). All scaling was on live or recently dead wood.
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Totals

Sweet Gum (Liquidambar styracifula)

Sector 1:         46

Sector 2:         8

Sector 3:         51

                        105         (84.68%)        

~15% had scaling on boles (a few of these were large trees). The majority of work was on crowns, including larger branches. Fallen trees were included when woodpecker involvement was evident and bark was tight.

Bitternut Hickory (Carya cordiformis)

Sector 1:            3

Sector 2:            4

Sector 3:            7

                           14         (11.29%)

All trees were standing; scaling was on boles and was very extensive (the tree shown on the homepage is one example) with one exception from this year . Insect tunnels were visible in all examples. An additional hickory with a modest amount of high branch scaling was found in Sector 1 this year but was not counted for this analysis.

Oak (Quercus) spp.

Sector 1:         1

Sector 2:         4

Sector 3:         0

                         5         (4.03%)

All oaks had scaling on large branches; one also had some on the bole. All oaks in Sector 2 were found in a single cluster.

We have some information on forest composition in Sector 3, and it appears that sweet gums make up approximately 19%, oaks upwards of 35%, and hickories somewhere under 10%. Sectors 1 and 2 may differ and be more varied in overall composition.

The overwhelming preference for sweet gums relative to their abundance stands out. The scaled oaks are a mix of species, one Nuttall’s, one willow, the others unidentified.

In Sector 3, I am treating the compact stretch from the location of Frank Wiley’s sighting last spring/downed sweet gum top where we had the camera trap to just south of our current deployment as a cluster. The estimate of 23 trees being found in this area is conservative. I have only found one instance of recent scaling north of the location of the downed limb/Frank’s 2015 sighting. The main cluster has been in the same vicinity this year and last, with additional work scattered around farther south. Two of the hickories are within 30 yards of each other, approximately half a mile from the cluster, and one was on the edge of the concentration.

It also may be significant to note that we found a cluster of old but intriguing cavities in the same vicinity as the Sector 3 concentration in 2013-2014. Most of these seem to have fallen. The difficulty we’re having finding active, suggestive cavities is vexing, and may be the most compelling reason to be skeptical about the presence of ivorybills in the area. At the same time, finding Pileated cavities is difficult, even in defended home ranges.

I’m treating Sector 1 as a single concentration; the vast majority of the work is on a natural levee where sweet gums are abundant. The entire area is considerably larger than the other clusters, but given the abundance and ease with which we’ve found sign there over the last five seasons, I think it constitutes one area of concentration.

In Sector 2, there was a small cluster in the area where I recorded putative kent calls in 2013, with work found in 2012 (spring and fall) and 2013. Because the area is small with open sight lines, I can be confident there has been no recent work there since late in 2013 (I last passed through it with Tom Foti back in March of this year.)

The sweet gum work Tom and I found on that day was perhaps half a mile north of this cluster, within 100 yards of the hickory on the homepage. The other hickories found in the 2013 and 2014 seasons were not far away, no more than 500 yards apart as the crow flies.

There’s obviously some bias here, since there’s a relationship between finding feeding sign in a given area and spending time there. Nevertheless, I have little doubt that the putative ivorybill work tends to be clustered. I also have little doubt about the strong preference for sweet gums, since I’m not looking at tree species when I look for scaling. The degree to which sweet gums are favored has only become clear over the last year or so.

Frank pointed out this data does not reflect most of the scaling that likely exists in relatively close proximity to the Sector 3 cluster but cannot be quantified because it is in an area we have intermittently visited due to  inaccessibility. Only two or three examples are from this area, which has been visited a handful of times.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Rare Ivory-billed Woodpecker Images

 

 

My visits to Cornell’s Kroch Library, where the Rare and Manuscript Collections are housed, have been very productive. In addition to the last letter to Tanner pertaining to the Singer Tract ivorybills quoted at length here, I’ve come across several little known ivorybill images, some better quality reproductions of the plates in Tanner, and some additional hints about ivorybill foraging excavations that I’ll discuss in a future post. I suspect that all of the images below are actually stills from the 1935 film footage that has been lost save for a few minutes. To see it, go here and start at 14:00. To the best of my knowledge, these images have not previously been published as stills, and a couple of the frames may never have been publicly available.

The first image is similar to the one that appears on Page 82 0f  The Race to Save the Lord God Bird.  This is a sequence (that apparently has been lost) in which the birds are changing places on the nest. A third image that follows the first two appears on p. 120 of The Race . . . A colorized version, at once gorgeous and crude and sadly somewhat damaged, is also included here; it’s reproduced in black and white in Jackson (p. 27).

I think the bird in the remaining frames is the male. In the second frame, he may be engaging in the motion described by Tanner, “. . . jerking as though working food from the back of its mouth.” the next frame shows the him peering into the cavity. These two images are clips from the surviving footage. The final shot may have come from a lost piece of film, since a remaining clip, filmed from a similar angle doesn’t include it.

In addition to the images posted below, two figures in Tanner’s dissertation include unpublished photos from 1938 – one of a male at the nest cavity and the other of a juvenile peering out of it. Those images may also be included in a future post. All four pictures below were taken with my iPhone. I have a high resolution scan of the fourth on order, since it is one of the best representations of presumed ivorybill excavation available. Images are Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library.

 

 

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Strips, Flakes, Chips, Chunks, and Slabs: Squirrels, Pileated Woodpeckers, and Ivorybills, Part 4

Careful examination of bark chips found in conjunction with extensive scaling is one of the key elements in our diagnostic gestalt, but “chips”, a term I’ve been using for years, is both inaccurate and too vague for what we believe is being left behind by Ivory-billed Woodpeckers and for differentiating it from the leavings of other animals. Tanner used “pieces” of bark, ranging “from the size of a “silver dollar to the size of “a man’s hand.” A caption from the National Geographic article on the 1935 Allen and Kellogg expedition that refers to “large chunks of bark”.  The existing images of these pieces of bark suggest that chunks is the better term.

It’s important to reiterate that this discussion applies only to live and freshly dead hardwoods. Pines slough bark quickly after death. The process is slower in hardwoods, but as decay progresses, the bark loosens considerably, with the rate of loosening depending on species and environmental conditions. Once the bark has loosened sufficiently, PIWOs can and do scale bark extensively, sometimes leaving behind large chips. In the images that follow (from Allen and Kellogg and Tanner), the bark chips ascribed to ivorybills appear to come from considerably longer dead trees than some of the examples we’ve found, but the images are informative.

Ivorybill Scaling Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

Ivorybill Scaling Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

The small tree shown above, identified as a “dead gum” by the 1935 expedition, appears to be a hackberry or sugarberry not a gum, and a fairly long dead one; the pieces of bark at the base resemble ones we found beneath hackberries or sugarberries in our old search area, some of which were considerably larger (the one below is the largest).

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This colorized slide reveals more about the bark at the base of these pines than the black and white print in Tanner (Plate 9).

There’s also this example, (Plate 10 in Tanner), which appears to be in a considerably more advanced state of decay, and presumably looser, than much of the work we find most interesting. I suspect most of the grubs were placed on the chip for illustrative purposes; the caption “Beetle larvae from beneath bark of Nuttall’s oak” is ambiguous as to where the larvae, which appear to be small Cerambycidae, were actually found.

What I think is most salient in Tanner’s description of bark chips is shape not size. In this regard, it seems important to come up with a more specific set of terms to replace the commonly used “chips”. I’d suggest using chunks and slabs for suspected ivorybill work (although smaller pieces of bark may also be present). Pileated bark removal can involve chips, strips, or flakes, the last when they’re doing the layered scaling discussed here and here. I suspect that squirrels remove hardwood bark primarily or exclusively in strips, and of course, their bark removal on cypresses leaves shredded bark hanging from the trees.

Let’s take a closer look at the differences among pieces of bark we have reason to believe were left by squirrels, those we have reason to believe were left behind by Pileated Woodpeckers, and those we suspect were left behind by Ivory-billed Woodpeckers.

I collected a number of bark chips from the tree we know to have been scaled by a squirrel, and while these were removed before our camera trap revealed the source, there’s strong reason to think they too were left behind by squirrels.

SquirrelChips

Note the uniformly elongated shape and the ragged appearance at the tops and bottoms of these strips of bark. This is not typical of bark that we infer or know to have been removed by woodpeckers, and it’s consistent with chewing, not scaling. The presumed squirrel strips I collected had the following dimensions:

9”x2.5”

7”x2.25”

5.75”x2″

7.5”x1.75”

4”x1.75”

The downed sweet gum from which they had been removed was a fairly young tree, and the bark is much thinner than on more mature ones. These strips were approximately 1/8″ thick. While this is a very small sample, we suspect (along with Houston from IBWO.net) that approximately 3″ is the upper limit for width when a squirrel is doing the bark removal.

Our research and observations suggest that Pileated Woodpeckers have two strategies for removing tight bark; one involves pecking around the edges until they can gradually pry off small pieces, and the other involves scaling away strips, sometimes in layers. Their physical structure precludes them from doing the extensive, clean scaling of tight bark that Tanner associated with ivorybills.

We suspect that this collection of chips, from a honey locust near a known Pileated nest, reflects the range of what the species is capable of doing on a tight-barked hardwood (and honey locust bark is relatively thin). The upper limit appears to be hand size, with many-quarter sized or smaller.

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The following are measurements of some fairly typical suspected Pileated strips from a sweet gum:

7”x1”

8”x.8”

7”x.8”

6”x.8”

The strips shown below, suspected Pileated Woodpecker leavings from a high branch, are on the large end of the spectrum for this category of work. The Peterson Guide is 9.5″ x 6.5″. I can’t rule squirrel out completely for these.

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Flakes resemble strips, but they are removed in layers, so that reaching the sapwood is a gradual process. Pileated scaling frequently has this appearance, something that seems frequently to be the case with congeners, including the larger-billed Black Woodpecker (Dryocopus martius).

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The chunks and slabs we suspect to be ivorybill work are significantly larger and thicker than strips, flakes and chips, although strips and chips may be present in the mix at the base of suspected feeding trees. Chunks are usually more irregular and varied in size and shape, and both chunks and slabs sometimes have what appear to be strike marks from a broad bill.

I kept one of the chunks scaled from the hickory tree on the homepage, a fairly typical example. It is 8.5″x3.5″ and .375″ thick. (It has undoubtedly lost some of its thickness after drying for over two years.)

Hickory2Chips

The sweet gum chunk with the apparent bill mark Frank is holding is 7.5″x3″ and .25″ thick. On mature, thicker barked trees most or all suspected ivorybill chunks, chips, and slabs will have been removed cleanly, all the way down to the sapwood.

Frank adds:

This particular bark “chunk” is intriguing on several levels. We have found that markings many describe as “bill marks” are really truncated galleries between the bark and sapwood. Marks made by woodpecker bills are distinctive, but somewhat subtle, and easily overlooked. This chunk actually has two interesting markings – markings that were left by the animal that removed the bark. The first is near the end of my left thumb – my right index finger is pointing toward it. It is about a quarter inch wide, a bit over a half inch long, and three sixteenths of an inch or so thick. The other is a “V” shaped “notch” at the end of the chunk, near the center of the photo. These places look as if they’ve been struck with a chisel – hard enough to rip the bark away from the sapwood/cambium. This suggests that, even though this bark was very tight, very few strikes were required to loosen and remove it. Granted that these marks are bill strikes, this suggests that the bird removing bark is indeed a powerful animal for its size. Back to Mark.

DSC00031The two preceding examples are on the smaller side for suspected ivorybill work; in the first, the density, tightness, and grain of hickory bark seem to be a limiting factor on size. Some of the larger examples are shown in the Bark Chip Gallery (as are several of the images shown above). A couple of additional examples of larger slabs are below. In the first, the oak was approximately 8 months dead (leaves attached), and the bark was still tight. (The fractured slab was damaged in transit.)

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Scaling and Squirrels: Part 2, Digging Deeper

Part 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:

  1. 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’. DSC00866
  2. Neck length. The much longer neck of the ivorybill allows for a broader range of motion.
  3. 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.

    Enlargement of image used for Tanner's Plate 13 showing foot structure. Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

    Detail of Tanner’s Plate 13 showing foot structure. Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

  4. 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.
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    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.

    Tailfeathers

    Middle Tail Feathers: Flicker, Ivory-billed, and Hairy Woodpecker

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    Pileated Woodpecker Tail Feathers. Note how the longest one resembles that of a Flicker more than that of an ivorybill.

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    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.

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detail

“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. ScalingNewArea

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.”


The Two Faces of James T. Tanner – A Study in Selective Memory and Blindspots

In a 1936 letter to James Tanner before Tanner began his survey of possible ivorybill habitat in the southeast, Herbert Stoddard wrote, “The area where they (Ivory-billed Woodpeckers) may occur at present is simply tremendous, not restricted as many believe.” Stoddard continued, “. . . if I had the rest of my life for the purpose, I doubt I could cover adequately half the ground I now think worth investigating. When I say adequately I have in mind five days I spent looking especially for these birds with men such as Bob Allen and Alex Sprunt on an area of some ten thousand acres known to be frequented by several pairs of these birds without seeing one. Of course this was due to the element of luck, as others have gone in the same area for a few hours and seen one or two. But it indicates the time one would have to spend in these great river valleys to really be reasonably sure that the birds were absent or even extremely rare therein.” Tanner was one person, and he clearly didn’t have the time to devote to the thorough survey Stoddard suggested, but the later record suggests that he failed even more deeply to take Stoddard’s words to heart. Stoddard’s perspective leaves room for the possibility that Tanner grossly underestimated the ivorybill population in his monograph, something that might lead to very different projections about the likelihood of survival today. It also sheds additional light on the difficulties in searching for ivorybills and on what appear to be some significant blindspots in Tanner’s thinking about the species.

I recently wrote a Facebook post in which I stated Tanner had a “hard time” finding Ivory-billed Woodpeckers. A very prominent American birder and ivorybill skeptic promptly shot back asking for citations, which I provided; I wouldn’t play along with the snarky response, but the exchange gave me the impetus to write this post. To most birders, Tanner is a kind of heroic figure, a pioneer ornithologist, and the author of the only in-depth, definitive study of the Ivory-billed Woodpecker, a bird that, in Tanner’s telling (and even more so in the retelling), was a super specialist that depended on virgin forest for its survival. Tanner is also rightly seen as having played a central role in the development of modern environmentalism, fighting to save the Singer Tract itself and later helping to create Congaree National Park, one of the few remaining substantial old growth stands in the south.

Those who are more deeply steeped in ivorybill lore are likely to have a somewhat different perspective, even as they admire Tanner’s good qualities. In later years, Tanner became increasingly dogmatic about ivorybill habitat requirements and was usually harshly dismissive of  reports from others – including John Dennis in Texas and Agey and Heinzmann in Florida. (This dismissiveness began to take hold in the early 1950s.) By no later than 1985, and probably much earlier than that, Tanner had become convinced the ivorybill was extinct, a conviction that he usually leavened with the statement that he’d love to be proven wrong. Ivorybill aficionados may also raise questions about the 1930s surveys he conducted in the southeast, and the rapidity with which he dismissed almost every place he visited as being unsuitable, sometimes based on a visit lasting a day or two. Most of these visits were made outside of breeding season, at times when finding ivorybills was considerably more difficult.

Tanner may have been right to dismiss many of these areas, but the possibility that he might have missed several populations cannot be ruled out, especially in light of the letter from Stoddard, an established ornithologist with first-hand knowledge of the species. At minimum, Stoddard’s letter put Tanner on notice that ivorybills could be very difficult to find.

Were preconceived beliefs driving Tanner from 1937-1939; was he being cavalier in his dismissals; or was he simply doing his best to accomplish what Stoddard said would take a lifetime in a few weeks spread over three years? It was probably all of the above, but whatever the reason, his mindset became an even bigger problem as time went on, leading him to foment the false impression that ivorybills should be easy to find, a notion that informed the views of my interlocutor on Facebook and of many those who believe the species is extinct.

The fact is that when Tanner was in the Singer Tract, the only birds he could find on a regular basis were the “John’s Bayou Family”, the group first studied in 1935. Their nesting and roosting grounds were approximately 1 mile from Sharkey Road. From 1935-1939, the birds nested in the same general vicinity. Three of the four nests were in very close proximity to one another, and the greatest distance between any two nest sites was 3/4 of a mile. Despite this clustering, it took Tanner five days to find a nest in 1939, when he didn’t have J.J. Kuhn (who had been forced out of his job as Singer Tract Warden) to assist him.

While Tanner paid respect to and credited Kuhn, the passage of time has made it increasingly clear that he downplayed the degree to which he depended on Kuhn to find ivorybills. Kuhn had been observing the birds for several years before the 1935 expedition (which also took several days to find ivorybills), and it’s reasonable to infer that the John’s Bayou family was already somewhat habituated to human presence by 1935. Certainly after ’35, they were accustomed to human activity in the immediate vicinity of their nest sites.

The only other ivorybill Tanner saw was one he named Mack’s Bayou Pete, presumably a bird hatched in 1935 from a nest that Kuhn found. As with the John’s Bayou pair, this bird was found within a home range that had been roughly delineated in 1935; Tanner believed he could recognize Pete’s voice, but the bird was far more frequently heard than seen.

Edited to Add: I’ve been reminded that the 1935 Mack’s Bayou Nest failed, and that Pete more likely fledged in 1937. The fate of the adult Mack’s Bayou pair is unknown. And that Tanner did encounter a wandering family group while watching the John’s Bayou birds. There was no indication of territoriality.

Tanner continued to correspond with informants in the Singer Tract until 1948 or ’49 and was advised that one or two birds remained until that time. As Tanner’s temporal distance from his experiences in the Singer Tract grew, so did the distortions in his memory. These distortions are perhaps most dramatically illustrated in an article he wrote entitled “A Forest Alive”, which was published posthumously in Birdwatch (2001), a British magazine. Prominent ivorybill skeptic Martin Collinson mentioned the article and quoted it at some length in a 2007 blog post:

http://proregulus.blogspot.com/2007/12/i-almost-certainly-ignored-this-article.html

Collinson concluded his post with this observation: “As others have pointed out… you can only rationalise the failure of the current searches if you don’t include the words ‘active and noisy’, ‘called frequently’ and ‘easier to see and follow’, in your dataset.”

Of course, Tanner’s observations applied only to the John’s Bayou birds studied in close proximity to a nest. More importantly, Tanner’s recollection was incomplete and inaccurate, and he corrected it in another, humbler, posthumous piece that appeared in Birdwatcher’s Digest (2000) under the title “A Postscript on Ivorybills”. Tanner began by observing that, “Like everyone else’s memory, mine forgets the annoying and unpleasant things and remembers the pleasing; the mosquitoes go but the birdsong remains. Mine is also likely to forget the important and regular events and retain the trivial and unusual.”

The article makes it clear that finding even the John’s Bayou birds (which had a known territory and roosting ground) could be difficult and was even harder outside of nesting season. Tanner concluded with this reminiscence: “Hunting in other areas of the Singer Tract for ivorybills was even more difficult and discouraging. My journal is full of such comments as ‘saw old sign, lots of impenetrable vines, and no ivorybills.’ The only other ivorybill we ever found outside of the one nesting pair and their offspring was a single male that we dubbed Mack’s Bayou Pete because of the area he usually inhabited. He was hard to find and once found was soon lost . . . ”  And to reiterate, Mack’s Bayou Pete’s home range was at least something of a known quantity.

By 1985, Tanner was advising the US Fish and Wildlife Service to classify the ivorybill as extinct. He gave the following reasons, to paraphrase:

1) The reports have been unconfirmed and they often describe behavior that is characteristic of Pileateds (flushing from stumps and logs).

Tanner described this as being rare in ivorybills, which may or may not be true, but it’s certainly not unheard of. Allen and Kellogg observed a female feeding on the ground. Moreover, not all reports involved this behavior.

2) There’s so much recreational use of areas where ivorybills used to be present that people should be hearing and seeing them, and there are no extensive areas of former IBWO habitat that are remote and unvisited.

What’s omitted from this analysis is the fact that the beginning of nesting season and the end of deer season are roughly congruent, at least in Louisiana. This means that there’s actually very little human traffic in many prime nesting areas during the times when birds are most active and vocal. And of course, the John’s Bayou area was not particularly remote, although other parts of the Singer Tract were considerably more difficult to reach.

3) Ivorybills are fairly conspicuous birds that, “if present . . . are not hard to find. Furthermore, the feeding sign they made (scaling bark from extensive areas of not long dead limbs and trees) could be easily recognized as a clue to their presence.”

With regard to the feeding sign, I have to wonder what Tanner would say about the sign we’ve found that appears to match this description perfectly. With regard to being easy to find, Tanner’s field notes and his reminiscence in “A Postscript . . .” make it clear that ivorybills were extremely difficult to find, except in extraordinary circumstances – in close proximity to a nest and perhaps with a good deal of habituation to human presence.

Tanner’s story is amazing. His monograph is seminal though not gospel. The in-depth examination of his work in Stephen Lyn Bales’s Ghost Birds is essential reading. Many of his later pronouncements, however, have done a disservice and continue to sow confusion more than two decades after his death.

I’m indebted to Fredrik Bryntesson for sharing Herbert Stoddard’s 1936 letter and reminding me of Tanner’s missive to USFWS. This piece is informed by years of discussion with Frank Wiley. He also made a number of constructive suggestions about the specific content. Direct descendants excepted, Frank was undoubtedly J.J. Kuhn’s greatest admirer.


Sweet Gums to Sweet Gums and More

In this post, I compared scaling on sweet gums in our search area with images of scaling on sweet gums taken by Martjan Lammertink in Congaree National Park; he has graciously granted me permission to post those images and some others here.

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Pileated Woodpecker Scaling on Pine – Photo by N. Banfield/Cornell Lab of Ornithology

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High Branch Scaling on Sweet Gum, Steinhagen, Texas – Photo by M. Lammertink/Cornell Lab of Ornithology

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Pileated Woodpecker Scaling on Sweet Gum, Congaree National Park, Photo by M. Lammertink/Cornell Lab of Ornithology

The focus of the original post was on the direct comparison between known Pileated Woodpecker scaling on sweet gums and the work we are finding in our search area. The differences are quite dramatic. In this post, I will simply include a number of examples of suspected ivorybill work from both our old and new search areas without too much discussion. The differences should be self-evident, even without reference to bark chips. I have come to believe that much if not all of the high branch scaling that Tanner presented as being typical and (by implication at least) diagnostic is not necessarily inconsistent with PIWO work. Thus, in the absence of other indicators, the Steinhagen photos are potentially interesting but not highly suggestive. Note that in all three images of PIWO work on boles, there is clear evidence that the bark has been removed in layers. This is true even on the pine, where signs of this layered work are visible on the left, just above the bird. I now suspect the absence or near absence of layering on extensively scaled, tight barked hardwoods may be the single most important component in the gestalt and may even be diagnostic in itself.

Even when the scaling is quite extensive, the signs of layering are likely to be a giveaway, as in this example from public land near our old search area. The bark chips around the base of this tree were all small and gave further indication that the work had been done in layers.

Presumed Pileated Woodpecker Scaling on Snag, East-Central Louisiana, 2011

Heavily Scaled Snag, East Central Louisiana 2011, Presumed Pileated Work

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Detail Showing Superficiality of Bark Removal – East-Central Louisiana, 2011

Pileated Scaling on Snag - East Central Louisiana 2011

Detail Showing Bark Removal in Layers – East-Central Louisiana 2011

Most of the images below have been discussed in other posts. The scaling is on oaks, hickories, and sweet gums and the differences in appearance should be self-evident.

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Scaling on a Hickory Snag, Louisiana, October 2013

 

Hickory3Top

Hickory3

Scaling on a Hickory – Top to Bottom – Louisiana, June 2014

MMHIckory2

Scaling on a Dying Hickory, Louisiana, May 2013

 

Oak1

Oak Scaling, Louisiana, October 2013

 

 

SP5140 scaled hickory (2)

SP5143 scaled hickory (2)

Spscaled hickory (2)

Hickory Scaling, Louisiana 2013 – Photos by Steve Pagans

HairyWPwork

FWHickory1

Hickory Scaling with eyed click beetle and Hairy Woodpecker work. We suspect that there may be a correlation between IBWO and HAWO foraging strategies.


Photo by Steve Pagans

Sweet Gum Scaling, Louisiana, January 2014, photo by Steve Pagans

ScalingNewArea

Hickory Scaling, Louisiana, June 2013

Heavily scaled young oak with suspected IBWO work extending from the base to well up on the trunk. Large bark chips are visible around the base of the tree

Heavily scaled young oak or sweet gum with suspected IBWO work extending from the base to well up on the trunk. Large bark chips are visible around the base of the tree

Extensive Scaling High on a Living Oak, Louisiana, March 2012

Extensive Scaling High on a Living Oak, Louisiana 2012

Detail of extensive scaling on oak

Detail of Extensive Scaling on Oak

Extensive Scaling on Live Willow Oak, March 2012

Extensive Scaling on Live Willow Oak, Louisiana 2012

Scaling on freshly dead oak, East-Central Louisiana, January 2010

Scaling on freshly dead oak, East-Central Louisiana, January 2010. Tree was extensively scaled including lower on the bole. Some bark chips were the size of my forearm

Sweet Gum Scaling, East-Central Louisiana, 2009

Sweet Gum Scaling, East-Central Louisiana, 2009


How The Ivory-billed Woodpecker Might Have Survived

I have been corresponding with Christopher Carlisle, a Mississippi birder who has recently started searching for ivorybills in the Pascagoula watershed. These exchanges, along with a post on IBWO.net about the Choctawhatchee, led me to start thinking, in a somewhat more methodical fashion, about habitat conditions and how the ivorybill might have survived and to consider the significant differences between the old Project Coyote search area and the new one.

I suspect there may have been three behaviors, probably operating separately and together, that made survival possible and detection and documentation difficult. These behaviors are consistent with the historical record, which suggests the species was considerably more adaptable than the simplified reading of Tanner that treats “virgin” or old growth timber as essential. Tanner’s own views on this issue became considerably more dogmatic over time, but even his early surveys of possible habitat in the southeast were influenced by this belief, which I’d suggest was more cultural than scientific, since Tanner was a product of an era in which frontier mythology profoundly influenced American thinking. Tanner’s description of the Singer Tract and especially his ivorybills are reminiscent of Edward S. Curtis’s Native Americans, magnificent, worthy of honor, but ultimately doomed and incapable of adapting.

The reality about Native Americans was considerably more complex of course, and the same goes for the Singer Tract. It was by no means a vast tract of virgin forest in the 1930s; much of it had been under cultivation prior to the Civil War, less than a century prior to Tanner’s seasons there. In pre-Columbian times, the southeast had a significant indigenous population, with perhaps as many as 5.2 million people in the Mississippi Valley alone. Thus, much of what was deemed to be “virgin” forest in the 20th-century was quite likely agricultural land in the pre-Columbian era. As I see it, Tanner’s preconceptions about what constituted “suitable habitat” led him to be somewhat cavalier, even in the early days – dismissing areas based on very brief visits, most often due to lack of “virgin” forest. As a result of this prejudice, Tanner may have underestimated the IBWO population.

This is not to negate the argument that IBWOs are more specialized than PIWOs; their morphology clearly places them in a different ecological niche, and their considerably more limited historic range also points to a higher degree of specialization. The fact that IBWOs do not regurgitate may place limits on behavior and home range during breeding season. The specialization, however, has far more to do with foraging behavior than with habitat requirements.

The IBWO.net post suggested (and implied some direct knowledge) that Geoff Hill and the Auburn team focused too heavily on the main channel of the Choctawhatchee. A person calling himself “Ranger Mike” wrote:

“During the last expedition by Auburn here on the Choctawhatchee River Basin I noticed two things that in my amateur opinion could have been better-First every time I saw researchers, or others who hunted and fished the area saw them, they were far to close to the main river. I am well aware of how hard it is access the flood plain areas, but the birds will likely be closer to the banks in the floodplains where there are very large old growth long leaf interspersed with the large cypress and gum that has been missed by logging due to its inaccessibility. This transition zone will be good habitat, and in my very significant time in these in both work and hunting/fishing has produced some interesting sightings and sign, with nothing of interest in the more frequently traveled areas. Second, I don’t think much time was spent on East Island. Its a very remote and promising area, but I think it was avoided because it would have required traversing by foot instead of floating around in kayaks or canoes.”

While I have not verified this account with anyone on the Auburn team, the general observation makes sense and is consistent in some respects with what Tanner observed in the Singer Tract. Nesting habitat was primarily located along tributary streams, not the Tensas River itself.

Edited to add: I have never been to the Choctawhatchee, and so have no first-hand knowledge with which to assess Ranger Mike’s comment. My intention was not to criticize Dr. Hill or the search efforts but to highlight a possible survival scenario. Since posting, I’ve heard from a couple of people with more knowledge of the area; one emailer stated that East Island is “way overlooked”, so if anyone’s interested in revisiting the Choctawhatchee, that might be a place to start.

The two Project Coyote search areas are quite different in character and forest composition. The current search area is secluded, very mature and surrounded by a good deal of contiguous lower quality habitat. It is part of a major watershed but is somewhat distant from the main river system, in the floodplain of a tributary. The old search area was on a small parcel of private land, about 3/5 of a mile distant from a medium-sized WMA, with bean fields in between. There are a number of larger WMAs in the surrounding area. The habitat in this area is mostly if not all of lower quality than in the new area and is discontinuous. Frank Wiley described it as “pearls on a string”. Assuming that ivorybills are or were present in both areas, it seems likely that the differences in habitat require different behaviors, and this may in turn point to how the species managed to persist post-Singer Tract. The following may be the behaviors that made survival possible.

Survival Strategy 1. Seek seclusion in remnant stands of mature forest and areas that were selectively logged, with substantial tracts of contiguous lower quality habitat associated; core habitats provide sufficient food supply during breeding season, and surrounding areas, pine plantations, younger upland hardwood forests and the like, might provide additional food sources the rest of the year. Examples of this type of area may include the Choctawhatchee, possibly other Florida rivers, the Carolinas, and the Pearl.

Survival Strategy 2. Expand home range substantially to forage in degraded habitat, using forested corridors to move around whenever possible but traversing open fields when necessary. This would entail having roosts and possibly nest sites near field edges in some instances, as appeared to be the case in the old Project Coyote search area, near Patterson, LA , a few other Louisiana locations, and possibly Wattensaw WMA in Arkansas. This idea is in part inspired by the November ’48 report to Tanner from Gus Willett, Singer Tract warden, saying that he saw a pair of ivorybills at “North Lake #1” and that the “birds are moving over a much larger area than formerly.” This is the last letter to Tanner pertaining to the Singer Tract, and it points to the likelihood that the widely circulated story of Don Eckelberry’s encounter with the last female IBWO is just another facet of the mythology that surrounds the species.

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Suspected recent nest cavity found by Frank Wiley near the edge of a bean field, East-Central Louisiana, 2009.

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Black and white image of tree in which suspected nest cavity was found. Compare with the appearance of this nest tree from the Singer Tract.

cavity 2 report

Close up of suspected roost cavity in a willow at the edge of a bean field. This cavity was in the tree where we obtained a Reconyx image of a possible ivorybill, discussed here.

Survival Strategy 3. The IBWO can function as a “disaster species”, as Dennis and others have argued, having a high degree of mobility when necessary. “Disaster” in this context could be a slow motion sort of disaster as in the Singer Tract, where sweet gums were undergoing a die-off, so this could include elements of either 1 or 2.

Strategy 1 would help explain some of the difficulty finding, relocating, and documenting the species, since these are remote and inaccessible locations and sightings would most often take place outside of core habitats. Strategy 2 might also help explain why detection is so difficult. These areas are sparsely populated, birds would only be in the open briefly, and would not stay in one place for long, except during nesting season. And as Frank Wiley pointed out, the main human activity during nesting season is turkey hunting, and David Kullivan notwithstanding, turkey hunters are unlikely to see ivorybills, in part because of where they’re focused and in part because their methods would be likely to be disruptive and cause any birds in the vicinity to flee.