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.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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.

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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 3, A Closer Look at Surfaces and Edges

The first two installments in this series, which was inspired by the discovery that squirrels are doing some of the bark scaling in our search area, are here and here. This installment will consider the appearance of the scaling itself, and the next will focus on pieces of bark; “chips” no longer feels sufficient to describe the spectrum of what we’ve found, and using more specific terminology may shed more light on what we think is diagnostic and why.

I’ll begin with the work we are now presuming to have been done by squirrels. In retrospect, it’s easy for me to understand why I was fooled by this bark stripping. I was not seriously considering mammals as a source due in part to the extent of some of the work involved; I never saw incisor marks on the wood, something that’s often described as being an important indicator; similarly, I have been unable to find these marks in the photographs I’ve taken of stripping that we now presume to have been done by squirrels.

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Tanner’s Plate 8, “Ivory-bill feeding sign on slender limb. Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

In addition, I was somewhat misled by Plate 8 and the description of what Kuhn thought was diagnostic that his daughter shared with us. (Scroll down in this post to see where my thinking went astray.) It’s my current view that Plate 8 could conceivably be squirrel work. Tanner doesn’t state that he actually observed an ivorybill doing the scaling.

Between 1937 and 1939, Tanner observed actual scaling a total of 73 times, but it’s not clear how many instances he might have photographed. In hindsight, the scaling in Plate 8 is not particularly impressive; the scaled patch is relatively small; the bark is thin and the hanging pieces may be an indication of removal by gnawing rather than bill strikes. Adhering bits of shredded bark and cambium are evident in some of the work we believe to be squirrel, including on the tree where we captured a squirrel stripping bark (albeit much smaller ones in that case).

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Small bits of bark and cambium adhering to downed sweet gum limb after presumed scaling by squirrels.

In fact, I think one of the keys to recognizing that squirrels are likely responsible for removing bark is a ragged, shredded, or chewed up appearance to the bark and cambium, as in the examples below.

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The information we got from Mrs. Edith notwithstanding, I am going to examine the edges of scaled areas more carefully and be sure they are for the most part cleanly incised. This is one of the main criteria for ascribing the work to ivorybills (although by no means all Campephilus scaling falls into this category, and some can have ragged edges). As I’ll be discussing in the next post, I think that bark chip characteristics provide an even better diagnostic.

Now let’s turn to targeted digging and the similarities between what we’re finding and the work of other Campephilus woodpeckers. In some of my previous posts on bark scaling I’ve mentioned “little or no damage to the underlying wood”. “Little” is the operative word here. In most if not all of the examples of scaling associated with large Cerambycid exit tunnels that we’ve been able to examine up close, there are also indications of targeted digging, and we have seen similar targeted digging on some of the higher branch work we’ve found. Targeted digging involves the expansion of individual exit tunnels in varying degrees. This can range from what appears to be little more than probing with the bill to deeper and wider excavations, but this excavation is incidental to the scaling, whereas in Pileated Woodpeckers, scaling on tight barked-trees is typically incidental to excavation.

A magnificent series of photographs by Luiz Vassoler posted to the Flickr Campephilus group, showing a Crimson-crested Woodpecker scaling and doing targeted digging, is illustrative (scroll through to your right for the whole series). This is not to suggest that other woodpeckers can’t or don’t dig for larvae in a targeted way, only it’s more suggestive evidence for the presence of Ivory-billed Woodpecker in our search area, given the context and what’s known about the foraging behavior of  its congeners.

I’ll keep commentary to a minimum and post some examples from our area (the seven photos immediately below) and then links to work done by other Campephilus woodpeckers.

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Pale-billed (on palm):There’s no scaling here, but the exit tunnels have been expanded vertically, and the expansions resemble some of the rectangular ones above.

Pale-billed (at nest): Very targeted digging and slight expansion of some exit tunnels.

Pale-billed: On a scaled surface, some tunnels expanded.

Robust: I’m including this almost as much for how well it shows Campephilus foot structure and the rotation of the fourth toe and hallux.

Cream-backed: Somewhat more aggressive expansion of tunnels on longer dead wood.

Red-necked: Targeted digging to the right of the bird.

Crimson-crested: Elongated dig into exit tunnel.

Crimson-crested: another great shot of the Campephilus foot. Targeted dig at bottom of scaled area.

Crimson-crested: Video showing targeted digging on an unscaled area.

Magellanic: are the most Dryocopus-like in the genus in terms of foraging behavior. Note their smaller bills and relatively shorter necks. They seem to spend a lot more time feeding near the ground and excavating large foraging pits than the other species, but they too do a considerable amount of targeted digging.

Magellanic: The appearance of the scaling here is strikingly similar to what we think is diagnostic for ivorybill. The tunnel at bottom right has been expanded, likely with the tip of the bill. It looks as though there is more targeted digging above and to the left.

The two images below, showing targeted excavations on small limbs, associated with extensive scaling on young, freshly ambrosia beetle-killed sweet gums, bear a striking similarity to work by Crimson-crested  (the long furrows in particular) and Magellanic Woodpeckers.

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One final and more speculative observation that might be of interest to other searchers. I had dismissed this work on a live maple as likely pileated because it is generalized digging, not scaling. After going through so many images of Campephilus foraging sign, I’m a little more intrigued by it, as I see similarities to sign like this and this. Like some of the work on ambrosia beetle-killed sweet gums, this almost looks like a hatchet had been taken to the tree; the wood was not at all punky; and red maple at 950 on the Janka hardness scale, while not nearly as hard as bitternut hickory (1500), is harder than sweet gum (850). While I’m not proposing this as a diagnostic, it may be more interesting than I initially thought.

Maple 1

Unusual excavation on live maple

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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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“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.”


More on Scaling and Squirrels, Part 1

This is will be the first in a series of 3-4 posts. The subject is multifaceted and subtle. Nuances can be hard to convey in words and accompanying illustrations; it’s easier to do in talks, with bark chips in hand to provide a more visceral sense of what’s being described. Still, it seems important to make the effort.

I realize now while my initial approach to evaluating feeding sign was rigorous, I grew somewhat lackadasical and overconfident. I also got distracted by the abundant scaling on downed sweet gums we started finding a year or so ago. I’m now confident that squirrels did much of this scaling, but the same does not apply to most of the other work we’ve found over the years.

Even before we discovered that squirrels were scaling bark on downed sweet gums (and quite possibly on standing trees as well), I was contemplating a post that broke down the bark scaling we’re finding into several categories. I was aware of having gotten away from the criteria I had laid out in the past and was feeling a desire to be more specific. That seems like a good place to begin, before delving too deeply into the nuances of distinguishing between squirrel and putative ivorybill work.

The following are the different types of interesting feeding sign we’re finding. Bear in mind that this pertains only to hardwoods that appear to be alive or recently dead and are known or suspected to have tight bark, except in cases where work appears to be old but still has characteristics that suggest it was done when bark was tight. The types of sign are ranked in the order of what I think is the likelihood that most or all of it is being left by Ivory-billed Woodpeckers, although the gap among categories 1-4 is small. (Frank would reverse categories 1 and 2.)

  1. Scaling on standing boles, low enough on the trunk to be examined up close. This includes both standing trees and ones with tops broken off. The sapwood of trees in this category has multiple large exit tunnels. The most prevalent species in this category is bitternut hickory, which has very thick, dense, tight bark, but we’ve also found it on sweet gums and oaks. This scaling is extensive and has a distinctive pattern that’s immediately recognizable in the field, an almost jagged appearance, although the actual edges are curved. The tree on the homepage is one example, and the image below illustrates how even when the scaling is not recent, this distinctive appearance remains. Bark chips are easiest to find for this type of work.

    Old scaling on hickory, 2015

    Old scaling on hickory, 2015. Note the exit tunnels and the absence of other woodpecker work, save for a small dig near the top of the scaled area.

  2. Scaling on standing boles, low enough on the trunk to be examined up close. Few or no large exit tunnels but signs of insect infestation under the bark. Superficial bill marks may be evident in the remaining cambium or on the surface of the sapwood. Tree species in this category include sweetgums and oaks. Chips are similarly easy to find.IMG_0144Lateral strike marks in the cambium
  3. Scaling that has the appearance of the work in category 1 but that cannot be examined up close. No possibility of examining bark chips.Hickory3
  4. Scaling higher on boles and lower branches of standing trees where exit tunnels may be visible, but close examination is not possible. In some cases, these trees are seen at a distance, across water bodies, so there’s no opportunity to look for chips. As is the case in categories 1 and 2, older scaling may go untouched by woodpeckers for extended periods. The first example below is recent; the second is probably more than two years old.
    Hickory3Top

    Top of scaled hickory.

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    Older scaling on dead top with exit tunnels.

     

  5. Scaling on higher branches of standing trees. Since these are often seen at some distance and in poor lighting conditions, it can also be more difficult to assess the freshness of the work, and the nature of infestation. Bark chips are usually much harder to find under these circumstances. Squirrels typically girdle limbs and often scale on the undersides of large, higher branches. Thus, when larger branches are at less than approximately a 70 degree angle, work on the underside may indicate a squirrel as the source, while the presence of extensive scaling limited to the upper side may be strongly suggestive of or diagnostic for woodpecker.BigSGLimb
  6. Scaling on downed trees or limbs that are at least in part more than 4’ from the ground.Detail of scaling on downed sweet gum.
  7. Scaling on downed trees and limbs that are mostly or all horizontal and less than 4’ from the ground.
    Work now suspected to squirrel on downed sweet gum.

    Work now suspected to be squirrel on downed sweet gum.

    IMGP0936

    Suspected Pileated Woodpecker work on same downed sweet gum

There’s an additional category that is somewhat different from the others. This involves work we’ve found on freshly dead, small sweet gums (>1’ dbh) with evidence of ambrosia beetle infestation. These trees have been stripped of bark, with some accompanying signs of excavation, ranging from targeted digging that resembles the work of Magellanic Woodpeckers (as on the left branch below) to the appearance of having been attacked with a hatchet. We think this work has strong potential for ivorybills, since we’ve found only three examples of it, in close proximity, and in an area with an abundance of other suggestive sign.HackedUpGum

It’s important to point out that when I use the word “scaling”, I am referring only to the clean removal of bark with little or no damage to underlying sapwood. While I have been quite adamant about this as a characteristic, some elaboration is probably in order, as my statements were made in reaction to woodpecker work that was often described as “scaling” in the early search years but was really bark removal in conjunction with excavation, something that’s typical of Pileated Woodpeckers. There still seems to be a good deal of misunderstanding on this subject, and the distinction is not always easy to communicate.

On close examination of some scaled areas, especially in category 1 but also in others, there are signs of targeted digging (but not deep or extensive excavation). This can range from a very slight expansion of an exit tunnel, apparently by probing with the tip of the bill, to what may be a harder strike or two, to a somewhat deeper but still targeted dig into the sapwood. Since many other species of woodpecker are capable of doing such targeted digging, I only consider this aspect when it’s in association with extensive, contiguous removal of bark. This will be explored in more depth in the next post in the series.

In category 1, known ivorybill prey species have been found under the bark or on the scaled surface of two trees. When exit tunnels are found on these trees in this category, they are consistent with infestation by large Cerambycid beetle larvae. I hypothesize that these trees are being scaled when the gregarious larvae have dug their exit tunnels but have not yet sealed their pupation chambers. This would be the stage at which they are most nutritious and most easily accessible for a species of woodpecker adapted to bark scaling, but the opportunity exists only within a very narrow time frame.

For several trees in categories 1 and 2, camera deployments of 2-4 months duration produced no return visits or evidence of what was doing the scaling; in a couple of cases Pileated Woodpeckers were photographed on the target trees for fairly protracted periods. In one, the pileated removed a few small pieces of bark, and in the other it appeared to do a little pecking and gleaning but did not remove any bark. We have revisited several of the other trees over periods ranging from months to two and a half years. One tree in category 2 (no tunnels) had a return visit approximately four months after the first one, when the bark was still tight. Several others, both with and without tunnels and including one first found in June of 2013 and re-examined during my last trip, had no obvious new scaling and little or no excavation of any kind, despite being in a more advanced state of decay

It’s also important to note that we have reason to believe that at least some of the work in all categories is being done by woodpeckers. For example, on the downed sweet gum shown above to illustrate category 7, found in November, there is obvious woodpecker work (likely Pileated) on the bole and apparent squirrel work on the upper limbs. Similarly we suspect woodpeckers did the scaling on the larger downed sweet gum (category 5) – mostly scaled higher but with some work within 4’ of the ground. I found this tree in May 2014, approximately 50 yards from the site of where we captured the squirrel stripping bark; while I do not recall looking for or examining bark chips, the edges of the scaled areas appear chiseled rather than gnawed, and the scaling on some of the higher limbs is on the upper side only.

The next post on this topic will examined the targeted expansion of exit tunnels and will revisit the similarities between what we’re finding and the work of other Campephilus woodpeckers. The following one will focus on bark chips and distinguishing between signs of gnawing and signs of scaling.


Squirrels Stripping Bark

I thought it was important to post the following advance of writing a comprehensive trip report.

On arriving in the search area last week, I found fresh scaling on a downed, recently dead sweet gum. The tree was relatively small, with a DBH of under two feet, and was alongside one of the roads that pass through our search area. There was fresh work on it on subsequent days. I staked it out on Thursday and saw nothing. We placed one of our game cams on it on Friday and retrieved it late Saturday. The trail cam photos showed a squirrel removing the bark fairly extensively. These images are currently in the game cam’s proprietary format, and we’ll post them in the near future.

As is the case with many of these blowdowns, there was also work in the tops that looked very consistent with Tanner’s descriptions of ivorybill scaling, although only on the upper sides of the limbs and branches. What this tells us is that we have to think squirrels are likely responsible for scaling on downed sweet gums and that all possible sign on downed wood should be looked at with a jaundiced eye. It also means that my previous foraging preference analysis has to be revised; we’ve taken that page private at least for the time being.

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Scaled area on bole of downed sweet gum. A squirrel expanded this considerably, working from left to right, toward the base.

I did not collect any chips that are unquestionably the work of a squirrel, but I did gather several that I presume to be. They measure:

9″x2.5″

7″x2.25″

5.75″x2″

7.5″x1.75″

4″x1.75″

and thus are all considerably longer than they are wide, stripped with the grain rather than scaled. The edges that go across the grain have a ragged appearance, and since the tree was not mature, the bark is thin and brittle compared to the bark of the mature downed top discussed below.

It’s odd that we only started finding this type of work in abundance in the past year; it doesn’t exactly match the diagnostic criteria I’d articulated earlier, but it comes close in some respects. It has been an unfortunate distraction, since the work on downed trees is much easier to find and photograph than work on the boles or upper branches of standing ones.

There was a little bit of fresh work on the downed sweet gum top found in April, but it was not extensive enough even to show up in the game cam images. There were a few chips on the ground, more like strips than chips, actually, 6′ to 8′ inches long and no more than an inch across at the largest. We’ve had numerous images of squirrels on that top but none showing them scaling bark for a period of more than two months. We got numerous images of squirrels again this time, and also a pair of Pileateds, with a Downy or Hairy (we didn’t examine the frames very closely) literally trailing the PIWOs up the trunk. In any event, there was no way to tell what did the little bit of scaling, or what did the scaling on the upper part of the downed top or the left fork, which had been almost entirely stripped before we got the camera on it. I lean toward this little bit of new  work was done by the Pileateds, but either way the chips don’t have the characteristics I associate with suspected ivorybill chips.

I had been planning to do a post refining and being more explicit about the different types of work I’d been ascribing to ivorybills. I still plan to go ahead with this project but will have to do so informed by this new information. I expect to write something later this month, after I’ve posted the trip report.

While squirrels cannot be ruled out for some of the work we’re finding, it seems unlikely that squirrels are doing all of it, especially on the boles of dense-barked, mature trees (like the hickory on the homepage and most of the others shown here) that have numerous cerambycid exit tunnels and on those that are not quite so freshly dead (and therefore don’t offer as much nutritional value). We monitored the tree on the homepage for several months and had no evidence of squirrels removing bark.

Some preliminary thoughts on what I think remains likely ivorybill work:

The chips shown in the bark chip gallery are mostly as large as or larger than an adult man’s hands. Chip size, shape, and density are probably factors that need to be looked at very closely, and perhaps the contrast between a very ragged, gnawed appearance and a cleaner one with apparent bill strikes is another key aspect.

This smashed sapling was clearly not worked on by squirrels, and the little patches of targeted digging on the small limb are highly reminiscent of Magellanic sign I’ve seen in several photographs:

https://projectcoyoteibwo.com/wp-content/uploads/2015/03/hackedgum2.jpg

If you zoom in on the image below, you can see that a woodpecker was involved because the tunnels have been expanded slightly and there’s one Magelllanic-looking dig on the smaller limb. This one also has some superficial scratches that could be from a bill:

https://projectcoyoteibwo.com/wp-content/uploads/2015/03/littlegumbottom.jpg

This work on a dead oak from the old search area remains interesting, because the bark chips were huge (one as big as my forearm) and due to the apparent lateral bill strikes that were evident when additional bark as stripped several months later:

https://projectcoyoteibwo.com/wp-content/uploads/2014/10/scaled-oak.gif

This little, dead gum (not oak, I think), because there are apparent bill strikes in the cambium and other obvious signs of lateral blows.

When it comes to high branch scaling, squirrels can do extensive damage, as in this example on a sugar maple. At the same time, some of the high branch work we’re finding shows clear signs of insect infestation and woodpecker involvement, as in this downed sweet gum limb I found on Saturday. The scaling took place before it fell.

IMGP1349

In next example, although the scaling has a little bit of the layered appearance we’ve suggested is more characteristic of Pileateds, it’s clear that woodpeckers are involved, since there are a few places where what we presume to be insect tunnels have been expanded.

IMGP0406

There’s also this one, which I initially thought could be due to natural sloughing, but how would sloughed bark fall at an upwards angle?swgumbole

While I was initially disappointed by this new data point, not only because it compels me not only to reexamine certain aspects of my hypothesis but also because it eliminates the types of targets we’ve thought most promising in terms of obtaining clear trail cam photos, I recognize that this is part of the process. It’s an opportunity to refine the hypothesis and a reminder to observe carefully. Ultimately, I think there’s more room for confusion between squirrel work and what I take to be IBWO work. We can’t help but wonder whether Tanner himself might have been fooled in some instances.


The Pros and Cons of Trail Cams

Frank wrote this up and asked me to post it.

Recently, we’ve received several messages, and another blogger has mentioned the use of game cameras – also referred to as trail cams, or camera traps – as aids in searching for Ivory-billed Woodpeckers. We’ve been deploying trail cams since early 2009, and have had some intriguing “hits”. They have been useful in many ways, and we have learned a lot about the feeding habits of other woodpeckers – specifically, Pileated, Hairy, and Red-bellied – that were useful in giving Mark insights into the type of feeding sign that we have come to believe is most likely diagnostic for ivorybills. In dozens of deployments, and hundreds of hours of searching with boots on the ground, and sometimes in the water, we have NEVER observed a woodpecker performing the type of scaling that we have come to suspect is diagnostic.

While trail cams are a valuable tool in our arsenal, they are, by no means infallible. There are many pitfalls involved in their use. Firstly, they are not designed to capture birds – in fact many common species of birds are almost unidentifiable in the images. Birds do not set off the motion triggers that these cameras use, and why should they? The cameras are designed for use along trails and adjacent to food plots used by larger mammals – usually whitetail deer. I have tested the Reconyx “Hyperfire” cameras that we use, and even a large Wild Turkey at fairly close range will not trigger one, even at its most sensitive setting, while a relatively small (terrier size) dog will trigger one from a distance of twenty-five or more yards. The manufacturer has indicated to me that there is “something about the way birds reflect light in the visible and infrared spectrum” that makes the cameras’ triggering units unable to “see” them.

As a result, ivorybill hunters must find a camera that will operate in time lapse mode. For all their disadvantages (3.1 megapixels, low resolution among them) the Reconyx cameras offer the best time lapse mode available at an affordable price. This, in and of itself, though, becomes a handicap, as the card for each camera must be programmed, using a proprietary program provided by Reconyx, on a PC. One programs the card, inserts it into the camera, and hopes for the best – there is no way to check and see if the card/camera combination is functioning properly. This has led to many wasted deployments. Additionally, there is the problem of how often should the camera take a photo vs. storage capacity of the card. The cams are designed for 8 gig cards, sometimes they will function with a 16 gig card, but will universally malfunction with a 32 gig card. 8 gigs is usually enough for a ten-day deployment with the camera time constrained to take a photo every twenty seconds for ten hours a day – you do get to select the hours of operation though. While every twenty seconds would seem to be quite often (and a full 8 gig card will store upwards of thirty thousand images), perform a little test for yourself. Go out to your favorite birdwatching location and see how long a bird – any arboreal non-raptor species – stays in one location for twenty or more seconds. Captures of birds on game cams are a relatively rare event – I have looked at nearly a million Reconyx photographs and have picked up birds of any kind in perhaps a thousand images – identifiable birds in maybe two hundred.

The very first thing that has to be done when using game cams is to select a location where you suspect an ivorybill is likely to show up. This could be a tree with scaled bark and other indications that an ivorybill has visited it, or a cavity with features that seem to match photographs of known ivorybill cavities. Both of these are, at best, iffy propositions. One has to find the tree, geotag it (you do have a good GPS unit, right?) then return to the location – often several miles of hiking through some pretty rough and secluded forest, carrying the camera and its mounting system – which weighs around ten pounds. Then the camera and mount have to be positioned to get the target near the center of the frame, which gets easier with practice, and the camera and mount hidden and intervening vegetation trimmed so as not to interfere with the line-of-sight. Once all this has been done the camera can be turned on, armed, and left to do its thing.

Assuming that everything up to this point has been done perfectly, in ten days or so, it’s time to change cards, or retrieve the cam. Now one is faced with the daunting prospect of going through some thirty-thousand photos looking for anything “interesting”. Often, several days of images will pass without a single “hit” of any kind. It’s often a relief to spot even a small woodpecker or squirrel, to remind one that the target is part of a living ecosystem.

The series shown here is exceptional in terms of quantity of images, quality, and our ability to place the camera. (It may be significant for what it doesn’t show, a Pileated doing the type of scaling we think is diagnostic.) Even so, it was not possible to cover the entire target tree.

As I stated earlier, these cameras, within their limitations, are useful tools, but for my money, nothing really beats the good old MK I MOD I human eyeball. But at this point, that’s just not enough …

In addition to the suggestive photos we’ve already posted, we recently obtained some pictures at the site where last week’s double knock was recorded. Because we find some of these pictures intriguing but inconclusive, we have deployed two cameras in hopes that the double placement will yield an identifiable photograph. The first picture, taken under good lighting conditions, clearly shows a Red-headed Woodpecker (there is a roost at the very top of the snag); the others are ambiguous. We are posting them unedited and leave it to you to speculate about what they may be. We recognize that none of these are of anywhere near good enough quality to be identifiable as ivorybills, but we are doing some further analysis to get a clearer sense of scale. The camera placement is 85’ from the tree; the branches behind the tree are an additional 15” away. My preliminary estimate of the diameter of the tree just above the jug handle on the right is approximately 18”.

I have taken careful measurements using a camera with known lens settings and a rangefinder – when the weather is more congenial, I will make comparison shots at the exact measured ranges. This should give a margin of error of ~1″ or less.

IMG_7153

IMG_4142 IMG_4195 IMG_4313 IMG_4399
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Rapid Evolution – I Think Not: More on Game Cams and Challenges

Cyberthrush’s blog has been an important resource for people with an interest in the IBWO for nearly a decade. I’ve agreed with him at times and have taken strong issue with him at others. His latest post falls into the latter category and strikes me as being somewhat irresponsible; it’s worthy of submission to The Annals of Armchair Quarterbacking. I responded in the comments but have some additional observations that seem better suited to posting here.

The inspiration for Cyberthrush’s post is an image someone sent him of suspected bark scaling low on a tree. The image is not shown in the post, but I suspect I’ve seen it and, if so, am sure it was the work of a mammal. In any case, he hypothesizes that the IBWO has rapidly evolved to live almost exclusively in the canopy. He uses the specialization of certain species – seabirds, Chimney Swifts, and warblers – to draw parallels, ignoring entirely that none of these species evolved nearly so rapidly. The only basis for this theory is the failure to obtain clear photographs.

He digresses to dismiss virtually all the photographs of feeding sign, cavities, and putative IBWOs and virtually every recording of putative kents or DKs he’s seen over the past 9 years. He writes: “I don’t want to discourage people from sending such things along, but I do want folks to know that the chance of getting a positive response from me is extremely slim . . .”

He goes on:

“I’m in the camp that believes any remaining IBWOs have evolved heightened wariness and caution, and as such DO NOT spend ANY extensive time at ground level, where they would be far more vulnerable. In fact, I believe they are now almost exclusively residents of the upper canopies, other than when flying from point A to point B and requiring a clear pathway. While they might land momentarily lower on a tree, they probably spend most of their daily lives minimally 35+ ft. high up (maybe 50+ ft.) on tree trunks/branches and inside cavities, well above levels frequented by Pileateds and other woodpecker cousins (and generally out of easy sight-line for searchers). It’s not clear to me how many of the remote automatic camera traps were ever set that high (though it’s clear several were not). Like Swifts in the air and Albatrosses at sea, I think Ivory-bills may spend most of their lives solely in the canopies… if you send me a photo of foraging sign or a cavity or a fuzzy bird lower than ~35 ft. high, I probably won’t take it too seriously (even though there are historical records of such cases), unless there are overriding additional details to catch my attention. If Ivory-bills currently lived and foraged below 35 ft. to any significant extent I believe we’d have the definitive evidence we need by now (well before now!); only perhaps as a denizen of the upper reaches might they be able to carry on successfully, while also evading encounters and detection to the degree they have . . .”

I don’t know who else is in his camp. Some have certainly argued that hunting pressure led the IBWO to become hyper-wary, and I can accept that hypothesis to some degree, although I think scarcity and the nature of the habitat have far more to do with the lack of conclusive documentation. The suggestion that the species evolved to exist almost exclusively in the canopy, when it was not infrequently seen feeding near the ground, is nowhere near as plausible, and it’s invented out of whole cloth.

As I wrote in the comments:

Your exclusion of any work below 35′ is arbitrary and wrongheaded, IMO. Forget Allen and Kellogg, Tanner even observed that they’re “not averse” to coming near the ground. Do you really think such a significant behavioral change evolved post-Tanner? An animal seeking food is going to go where the food is, and as it happens, the largest quantity of food is often to be found in the boles. I agree that cavities will be high up and also that work that’s exclusively near the base of the tree is suspect, but when the work goes higher than about 10 feet you can pretty well rule out a mammalian source (unless giraffes are around or there’s some heretofore undiscovered porcupine species in the swamps of Louisiana and Florida). When it’s very extensive, you can be pretty confident that it’s either PIWO or IBWO, and as I’ve argued at length on the Project Coyote blog, I think there is a limited range of work that is identifiable as IBWO.

This really is giraffe foraging sign, photographed in Louisiana . . . Long story.

This really is giraffe foraging sign, photographed in Louisiana . . . Long story.

One avian example of rapid evolution (though not nearly so rapid as Cyberthrush’s IBWO) is the Cahow, but that adaptation involved a change in nesting behavior due to a lack of adequate sites, something that’s far more akin to the kinds of survival strategies discussed in this recent post. There’s simply no reason to think that IBWOs could have suddenly evolved to live almost solely in the canopy. Not when Allen and Kellogg even observed one feeding on the ground; not when Kuhn observed one feeding a foot up; not when one of the clearest photos of bark scaling shows the work going to the base of the tree (the bark chips in this image are worth a close look, and they resemble many that we have found.)

With regard to aiming cameras at the canopy, I discussed the limitations of game cam technology in this post. The challenges increase dramatically when the cameras are aimed even higher, as is illustrated in this photo of a bird about 75’ up in a tree. There’s simply no way to get a conclusive ID. I think it’s suggestive of a female IBWO and that red would be visible in the crest if it were a PIWO, although it’s clearly nowhere near as intriguing as our other two Reconyx photos. Frank disagrees and thinks it could be anything.

IMG_9463 Red Box

Reconyx image and detail. Old Project Coyote search area, March 2009

Reconyx image and detail. Old Project Coyote search area, March 2010

Either way, aiming these very poor resolution, short focal length cameras high complicates matters exponentially. The likelihood of getting a clear image at such a great distance and with backlighting is infinitesimal. Aiming high is likely to be a wasted effort. One final note about game cameras, Cyberthrush attaches a great deal more significance to the lack of photos than I do. As far as I’m aware game cameras were only extensively deployed in Arkansas, South Florida, and the Choctawhatchee. They’ll only work if they’re deployed at the right time and in the right place, something that’s much easier said than done. As I’ve mentioned previously, virtually all the scaling we’ve found seems to have been done in a very limited number of visits to the tree, perhaps just one, and in the very rare instances where we’ve found evidence of a return of whatever removed the bark, there has been a gap of several months between visits.

The key to all of this is going to be finding a roost or nest site (unless someone gets extremely lucky.) I’m convinced that feeding sign is what can point searchers in that direction; it’s what led Kuhn and the Allen and Kellogg expedition to birds in the 1930s. That’s the reason for my focus on it. Cyberthrush does a disservice to all searchers by suggesting, based on unfounded speculation, that virtually anything found below 35’ feet is not worthy of attention.

Heavily scaled young oak with suspected IBWO work extending from the base to well up on the trunk.

Heavily scaled young sweet gum or oak with suspected IBWO work extending from the base to well up on the trunk. Note the large bark chips at the base.


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.

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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.


A Bark Chip, BIll Strikes, and Specimens: Four Images from 2010

For those who missed them, I thought I’d repost these images from 2010. The bark chip is from the old Project Coyote search area.

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PWIO bill chip