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More Squirrels and No Scaling on a Mature Sweetgum

I have reviewed the entire late August-late October card and some of the June-August card for what we’ve designated as deployment 5 – a three-years dead Sweetgum stub discussed last summer. Based on approximately six months of data from this deployment, I think squirrels can be excluded as the source of extensive bark removal from mature, thick-barked hardwood boles, just as the data suggest that Pileated Woodpecker can be excluded as the source of scaling on hickories.

The only potential sources of the extensive bark removal under discussion are gray or fox squirrel, Pileated Woodpecker, and Ivory-billed Woodpecker. Pileated Woodpeckers appear to be unable to remove large quantities of bark from hickories in large pieces, and squirrels appear to be unable to do so on the weaker, thinner-barked sweetgums. Based on trail cam captures obtained thus far, Ivory-billed Woodpecker is the likeliest source for the extensive bark-scaling on hickories that we’ve found infrequently in our search area and that I’ve hypothesized is diagnostic for that species.

There were no woodpecker hits on this target tree, but there are multiple sequences involving squirrels. There was minimal little bark removal, and only from previously scaled areas. In fact, I have only detected one visible change to the bark. A small quantity was removed on June 9, between 11:44:13 and 11:44:33. This is shown in the details below.

Squirrels were active on this scaled patch over the course of the deployment, but whatever removed the small strip of bark on the lower right did so during that 20-second interval and was not captured on the trail camera. I think a woodpecker of some sort is probable, since a squirrel would likely have been visible on the trunk in preceding or subsequent frames.

More importantly, squirrels were captured on or around the scaled areas on multiple occasions, and the captures shed light the way they interact with bark on standing boles and what may limit their capacity to remove it.

This deployment ran from August 19-October 21. Squirrels were detected on 17 days and on or near the scaled surfaces on at least 6 of those days. As previously documented, squirrels displayed interest in the edges of the scaling and frequently appeared to be gnawing; however, they removed little or no bark. We now have numerous captures of squirrels on target boles, both scaled and unscaled, and no captures showing them removing bark in quantity or in anything other than small strips.

Squirrels are clearly capable of rapidly and efficiently removing bark from limbs, downed trees, and thinner barked boles. However, I think there are physical limits – body structure and incisor length – on their capacity to remove thick bark from standing boles.

The following images and time lapse clips show what squirrels do when confronted with thicker bark and suggest that when hanging onto a standing trunk, they lack the leverage to remove bark quickly and leave large pieces behind. This should apparent in the selection of stills and video clips shown below as well as in the sequences posted previously. (A brief discussion of squirrels on hickories follows the images.)

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Up to now, I have not been differentiating among squirrel hits on targeted trees, squirrel hits on or near scaled surfaces, and squirrel hits in other parts of the frame. Suffice it to say there many, far more than woodpecker hits on both sweet gums and hickories. Squirrels frequently show an interest in the scaled surfaces and also in other damaged areas (like the fracture in the hickory bark shown below). To date we have no examples of squirrels removing any bark from hickories, regardless of condition. It stands to reason that the limits of their capacity on hickories would far exceed what limits their capacity on sweet gums.

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Evidence Part 1: Project Coyote 2009-2018

Summary

Evidence collected by Project Coyote in two parts of Louisiana from 2009-2018 should, on its own, suffice to justify maintaining the Ivory-billed Woodpecker’s current listing as an extant, endangered species in the United States. Others may differ, but I think the totality of the evidence does even more, making a compelling case that the species persists in more than one Louisiana location.

Introduction

This will be a two part post. The initial impetus for writing it was a conversation I had with Erik Hendrickson about how the scientific, birding, and legal approaches to evidence seem to differ. That will be the main focus of Part 2. As for Part 1, after talking to Erik, I realized that I’d never done a single post aggregating the evidence we’ve obtained over the years, so when it was announced that the U.S. Fish and Wildlife Service would be conducting a status review for the Ivory-billed Woodpecker, the need for writing this up became more urgent. That’s the primary focus of Part 1, but some of what I’m planning for Part 2 will be foreshadowed in this lengthy treatment.

There is a strong tendency to privilege visual evidence over other forms – audio and circumstantial. I’m inclined to think that our audio evidence is the most compelling material overall; as regular readers know, I also think circumstantial evidence, feeding sign in particular, is very important. But the structure of this post will track conventional attitudes, starting with visual material followed by a discussion of sound recordings and auditory encounters, and concluding with more circumstantial forms of evidence.

Locations

Project Coyote has been focused on two areas in Central and East-central Louisiana. I found what I call the “old” search area after reading a newspaper account of a local landowner’s efforts to get his reports taken seriously. This is the landowner who sketched corrections to the Louisiana Hunting Guide’s ivorybill illustrations and who showed Frank Wiley (my late collaborator) bark scaling when he visited the area.

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To be clear about what he was trying to show in the corrections: the gentleman died before I had a chance to meet him, but as Frank told me after his August 2009 interview, all of the corrections are in red ink, so the intent was not to put a male crest on a female bird; it was to show the female’s crest as more erect and recurved than the drawing and indicate that the male’s crest also is more erect and prominent (less Pileated-like) than the game guide representation. Also note the drawings at top right, in which he compared IBWO and PIWO wings, implying that the wings in the game guide image are a little too rounded.

What’s most salient about these observations is not whether they are perfectly accurate, although they do seem to reflect some little-known nuances, it’s that the landowner had enough claimed observations of male and female ivorybills to recognize subtle differences and to distinguish them from Pileateds. In addition, he was offended by the treatment he received when he tried to alert the authorities. I have personal knowledge about this last aspect based on conversations with family members who wanted to see him vindicated.

He was certainly convincing enough for Frank to start visiting the property on a weekly basis during the summer of 2009. Thus, Project Coyote was born.

The landowner’s reports go back to the 1990s. (The linked post includes audio from 2009). There are several medium to large state WMAs and National Wildlife Refuges in fairly close proximity to the site. We heard additional claims from residents of the area while we were focused there.

Putative ivorybill activity on the property seems to have diminished or ended altogether after an adjoining parcel was logged in late fall 2010. As a result, we gradually shifted our attention to the new search area.

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The old search area received minimal attention during the post-Arkansas period; some peripheral Ivory-billed Woodpecker-related research was conducted in the general vicinity, but there was no formal, funded search effort. Nor was it visited by Cornell’s Mobile Search Team, although Martjan Lammertink did spend several days on site, after the logging.

Similarly, our “new” search area was entirely off the radar. It doesn’t show up on anyone’s list of promising locations, notwithstanding the fact that it is in one of the most sparsely populated, heavily forested parts of the state. There’s also a long history of local reports. Most of the claims seem to have been fairly recent, but some go back to the late 1990s.

And these are only the claims I know about . . .

Eyewitness Evidence

For reasons that I hope will become clear, I have not kept track of all our possible sightings since 2009 and have not always mentioned them in blog posts. Nevertheless, I’ll begin with sightings. Over the years, Frank had more possibles and reported having better views than anyone else. I’m probably second, with approximately six since 2009, but unfortunately no good looks. Steve Pagans has had several possibles; a few visitors have also made claims.

While this is largely a subject for the next post, it’s well-known that eyewitness testimony is unreliable, at least when the source is an untrained observer. Nevertheless, eyewitness testimony is central to many a criminal trial, and it has a strong impact on jurors. There seems to be a parallel with respect to the ivorybill. Accounts of possible sightings tend to attract more interest than many more substantive and important posts.

Thus my Sunset Sighting post, which is not quite two months old, has had approximately 800 pages views, but my March 18, 2017 post entitled, Numerous Kent-like Calls Recorded on March 11 and 15, 2017 received a total of 744 views last year. Similarly, the post on Joseph Saucier’s October 2017 sighting and our follow-up visit to that location, Change of Pace Change of Place, posted in late November, received 804 page views, the second highest total for the year, (well behind the announcement of Frank’s passing).

According to a survey conducted in the aftermath of the Arkansas controversy, “[R]espondents were most confident in the sightings, less confident in the Luneau video and recordings of double-knocks and kent calls, and least confident in the FishCrow video.” The discrepancy was strongest for the “Definitely of IBWO” category, where 22 people listed sightings as conclusive, compared to 10 for the Luneau video, 9 for kent calls, 8 for double knocks, and 4 for the first Fishcrow video. (PDF) The Great Ivory-billed Woodpecker Debate: Perceptions of the Evidence. Available from: https://www.researchgate.net/publication/259337980_The_Great_Ivory-billed_Woodpecker_Debate_Perceptions_of_the_Evidence[accessed Jun 28 2018].

So sightings have an almost irresistible appeal; in some cases, there’s good reason to credit them, but it is very difficult to separate the wheat from the chaff, to determine what’s trustworthy and what isn’t. And there are many kinds of chaff – wishful thinking, self-delusion, ignorance, mistake, and deception to name the most obvious.

I’ve retrospectively rejected a couple of my possible sightings (and almost did so with the recent “Wooden Wings” incident), partly because I’m disposed to look for reasons to doubt myself and partly because I realized that I was in some way primed in a couple of those instances; for example, in one case, I’d been looking at specimens the day before.   In the absence of a good look, I think it’s better to err on the side of self-skepticism.

When it comes to claims from others, it’s impossible to know with certainty what someone else saw, even when reports are accompanied by detailed sketches and field notes, as is the case with several of Frank’s sightings. I was with him for one, on April 3, 2015, when he made notes (available at the link) and a sketch (at my urging). I have no doubt that he was convinced he saw an ivorybill, as he was visibly shaken immediately afterwards and was very slow to regain his composure.

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But I really like corroboration, and to the best of my recollection, Frank and I had two possible two-person sightings in all our time together – the first was in the old search area, the day after an auditory encounter and a week before a suggestive trail cam capture was obtained, effectively from the same spot. I consider this my strongest possible sighting.

The second was much weaker, a flyover with two birds seen in silhouette within 15-20 minutes of an ADK series. (Three of my possible sightings, two of which Frank also saw, have been associated with ADKs.) We did not think much of this possible at the time but could not explain it away entirely. I should add that Frank had several other two or more person sightings, but I was not present for those.

With regard to the local reports, I’m always mindful of the possibility that I’m being played, especially as an obvious northerner in rural Louisiana, but I don’t think that has ever happened. It’s still necessary to listen closely and ask the right questions. Pileated, Red-headed, and even Red-bellied Woodpeckers can be confusing for non-birders. I’m more likely to credit accounts from people who make it clear they know Pileateds and know the difference (like the landowner in the old search area) or from people who say they thought the ‘ones with the white backs are the males’ and the ‘ones with the black backs are the females’. I’ve heard this only a couple of times. But I like it best when we get ivorybill claims from different, unconnected people referencing the same location; this has happened in the vicinity of the current search area.

To conclude, members of our group have had multiple sightings of varying quality, in two different Louisiana locations since 2009. In addition, there have been multiple claims from locals in both areas.

One final note, relevant to the USFWS review: I am aware of a number of additional post-2009 claims from Louisiana (and a few from other states). In a couple of cases, Frank interviewed the people involved and found them to be credible. A cellphone video was obtained in one instance; the observers’ excitement over apparently seeing a pair of ivorybills is evident, but the quality of the video is extremely poor. In the other case, two people saw the bird and one provided a highly detailed description and sketch. There’s also Joseph Saucier’s report from last fall; our follow-up suggested that much of the habitat in this large expanse of forest was likely suitable, and Matt Courtman, who is an excellent birder, heard what he thought was a very good double knock on one of his follow-up visits.

Photographic Evidence

I recently posted a couple of Frank’s 2009 sightings and accompanying photographs that hadn’t been made public previously. These are the only photographs associated with possible sightings that we have obtained. Full details are available at the link; rather than recapitulate them here, I’ll focus on trail cam photos, including several that have been discussed previously plus a few intriguing ones from the old search area that have not been posted previously.

These are the images I think are most strongly suggestive of Ivory-billed Woodpecker and for which I am unaware of a strong counterargument.

The first two have been discussed repeatedly at length in a number of other posts. Both are from the old search area; the first was taken in August 2009 and the second, which appears to show a female Ivory-billed Woodpecker, was taken in late November, a week after the sighting discussed in the previous section.

To reiterate a couple of points about the August 2009 image: in the original photograph, there appears to be some red in the crest (though it’s not positioned right for either PIWO or IBWO). Careful review and image enhancement made it clear to me that the red is an artifact and the crest is black. In addition, as shown in the enhanced detail, there appears to be a large, light-colored bill protruding from a cavity in the background. This apparent bill is absent from captures obtained on other days. It changes position in the two frames where it is visible, suggesting it is attached to something within the cavity. (Unfortunately, the other frames from that morning have long since been lost.)

The image of a bird in flight, from the new search area, is more problematic, as it is not demonstrably a woodpecker. The still above includes an inserted Imperial Woodpecker for comparison, with motion blur reduction applied to the bird captured by the trail cam. One prominent birder stated that it is a Blue Jay, but as discussed in the original post, the bird is behind the snag and appears to be as large as or larger than a Pileated Woodpecker captured on the trunk.

Although we’ve determined that one of the initially intriguing images from that deployment shows a Red-headed Woodpecker, a few others remain interesting.

There’s an additional image from the spring of 2010 (old search area) that has always intrigued me, though I never had a chance to examine the original. I think it shows a large woodpecker, with a black crest, high on a honey locust. If it were a Pileated, male or female, I’d expect some red to be visible in the crest, even under these conditions.

Finally, there are a couple of additional trail cam captures from the old search area that I have not posted previously. By now, the original sequences are lost, and I’ve long since forgotten any details or discussion we might have had when Frank sent me the images. While they are far from conclusive, I think they are interesting enough to post in this context. At minimum, they further illustrate the challenges associated with obtaining definitive trail cam imagery.

Audio Evidence

Note: If you listen to the recordings below with headphones (recommended) be aware that some have loud sounds, clarinet toots and ADKs, in the foreground. This applies to the clip from March 2013 that I recorded and to many of Matt and Phil’s recordings from March 2017.

Possible auditory encounters far outnumber possible sightings, and over the years we have made numerous recordings of putative kents and double knocks (more than once in combination, which should add to their evidentiary value). Some visitors have been rewarded by hearing something within a day or two of arriving, and this has been true in both search areas, although others have been less fortunate, and I heard nothing suggestive during the most recent field season (though Matt Courtman recorded three possible calls in April of this year).

I will not be including all the audio evidence we’ve obtained, just some of the material I think is most significant. Some of the putative kent calls that have been recorded over the years may be Blue Jays; it has been suggested that Matt’s calls from this spring are too low pitched for ivorybill and might be from a heron, though I think they come from the same source. Regardless, many of the calls are simply inconsistent with any known bird species, are fairly close to the Singer Tract recordings harmonically, and are perfectly consistent with written descriptions of Ivory-billed Woodpecker sounds.

One of the most dramatic encounters involving both apparent kents and double knocks was from the old search area. It seemed to have been triggered by banging from the tin roof of an old deer stand. Six people were present, and much of the incident was recorded. There were apparently two birds involved. More details are in this post, and here is Frank’s 58 minute recording:

Extracts from the encounter and other material recorded in person and on remote units in the old search area and environs, as well as sonograms, can be found here, via the Wayback Machine. Some of the Wayback Machine links are not functioning, and the material posted there includes a couple of double knocks; here are several of the recorded kent-like calls:

Note that the fundamental frequencies on many, but not all, of these calls are in the 900-925 hz range, higher than the Singer Tract recordings and possibly consistent with Blue Jay. But in the second clip above, the fundamentals of both the lower calls at the beginning and the higher calls at the end appear to be a little over 800 hz., and during the extended encounter mentioned above, the calls went on for a prolonged period without the source revealing itself as a Blue Jay, which would be typical if the animal were indeed a jay.

The same applies to calls I heard and recorded in the new search area on the morning and afternoon of March 2, 2013. The morning calls went on for ~20 minutes. I did not think they were Blue Jays in the field.

We have recorded apparent double knocks in apparent reaction to ADKs and to Barred Owl calls and sometimes in contexts where the trigger is unclear, as in this example from an October 2015 post written by Frank:

“Bob and I continued upstream for another half mile, located a nice spot with a good view, and I performed an ADK series, followed about ten minutes later by a series of electronic playbacks of Singer Tract ivorybill calls. Shortly thereafter, Bob heard a double rap drum, that was captured on my digital recorder. I personally don’t believe that the drum was a direct response to my ADKs as there was at least a fifteen minute interval after the last of the ADK/playback series.

The double rap is not “perfect” in that the “intra-knock interval” is about .05 seconds longer than the “ideal” – based on averages of the intervals of other Campephilus drums – but it sounds very good.”

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The 15 minute interval between ADK/playback and apparent response is similar to the lag time that has been observed in other Campephilus woodpeckers responding to ADKs; it may be worth distinguishing between a slower ‘response’ and a more immediate ‘reaction’ in this context. (M. Lammertink, pers. comm.)

In my view, the audio recorded by Phil Vanbergen and Matt Courtman in March 2017 is compelling, perhaps the most compelling evidence we’ve obtained. On the morning of March 15, they recorded over 200 calls, along with a number of possible double knocks, over an approximately three hour period. The calls have lower fundamental frequencies than many of those in earlier recordings; these frequencies are considerably lower than any kent-like Blue Jay calls I’ve been able to locate online. Other suggestions have included, Red-breasted Nuthatch (too high) and Wild Turkey (no typical Turkey vocalizations were recorded that morning).

Overall, the calls appear to be inconsistent with any other known species of bird, mammal, or amphibian. Their association with Campephilus-like double knocks strengthens the argument for Ivory-billed Woodpecker as the source. As far as I know, the sheer number of recorded calls is unprecedented for a single incident in the post-Singer Tract era.

I was lucky enough to hear a couple of the calls on March 11, the day Phil first captured them, along with a couple more and some knocks at the same location on the following day. I’ve blogged about these recordings at length in multiple posts; I won’t repeat all that material here, but the discussions are worth reading. I will repost some of  the original recordings and enhanced versions.

Here is the first recording Phil made, one clip with the calls isolated and one with our talk and reactions. It may be difficult to hear the calls without headphones.

Here are some brief extracts from Phil’s March 15 recordings:

Here are some from Matt’s:

In the interest of brevity, I encourage readers to visit this post for in depth analysis, various extracts, and amplified versions that highlight the calls and some of the knocks. As always, it helps to listen through headphones.

Indirect Evidence: Bark Scaling, Bark Chips, and Cavities

I’ve discussed my bark scaling hypothesis – that a certain type or types of scaling may be diagnostic for Ivory-billed Woodpecker – multiple times over the years. As explored in a couple of recent posts, we are in the process of testing it. I won’t recapitulate the hypothesis here except to say that I remain convinced that neither Pileated Woodpeckers nor squirrels are physically capable of removing hickory bark in the manner we’ve found in the new search area. There may be other diagnostic characteristics, but my main focus is now on the hickories, since the work on that species is the most extreme outlier. Below are some dramatic examples of bark scaling (plus one image of interesting feeding sign on a sweet gum sapling that had been stripped of bark) on hickories, oaks, and sweet gums from both search areas.

For Tanner, bark scaling was one of the strongest indicators of ivorybill presence, even though he accepted some reports from trusted sources in areas where he found no scaling. The absence of scaling (along with poor habitat “quality”) was one of his main reasons for dismissing reports during his 1930s survey and rejecting the ones from the Big Thicket in the 1960s. He also doubted reports from the Chipola and Apalachicola area in 1950 based on finding no cavities or scaling during a 4 day visit. He concluded his notes on the trip by stating:

Conclusion: No I-b now in Chipola R. and neighboring Apalach R. swamps. Many of Kelso’s reports are mistaken, – not deliberately false, but due to ignorance and wishful thinking. There appear to be contradictions in some of his stories. I could not get any clear statement of what Ivory-bills sound like from him. He said that the local name of I-b was “Saddleback”, – which appears good but in many ways odd. Also “Van Dyke”! There certainly is no fresh sign in any area we visited indicating that the birds are present. The only possibility is that of scaling on pine; this may be solved by watching Pileateds in the pine woods.

(F. Bryntesson, pers. comm.)

While I think it’s possible, indeed likely, that some of the work Tanner ascribed to ivorybills was done by Pileated Woodpeckers and squirrels, there’s no question that an abundance of bark scaling is relevant in assessing possible ivorybill presence in a given area.

Based on visits, some lasting a week or more, to suspected ivorybill haunts in South Carolina, Florida, and Louisiana and on information provided by other searchers and people who have spent years in southeastern forests, I feel safe in saying that the quantity and quality of bark scaling found in both search areas is unusual. We also found an abundance of scaling in the area where Mr. Saucier had his sighting last year, something that I think lends added credibility to his report.

In the past, many in the searcher community speculated that lateral groves or bill marks in the cambium or sapwood might be suggestive, but this view has fallen out of favor; much of what was thought to be “scaling” in these instances was in fact shallow excavation with associated bark removal. We found one example of superficial lateral marks in 2013 that continues to intrigue me, although the snag in question is a young sweet gum that could easily have been stripped by a squirrel or Pileated Woodpecker.

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The edges of the scaled area may tell more of a story, especially in conjunction with any bark chips found on the ground. On the trees shown above, damage to the still-adhering bark suggests that lateral blows were integral to the scaling. This would be expected if the source were a Campephilus woodpecker.

An abundance of large, hard, thick bark chips (or chunks) around the base of a tree is also a likely indicator. Pileated Woodpeckers and squirrels seem to remove bark in smaller pieces and in strips. Additionally, when squirrels are involved and the bark has  been recently removed, it’s likely that there will be a lot of smaller debris in the mix, since squirrels have to gnaw their way through the bark. Some of the chips we found in the old search area seem to have bill marks consistent with Ivory-billed Woodpecker.

The bills of specimens, at least, seem to fit perfectly into indentations in the chips, but Pileated Woodpecker bills seem to be too small. The larger chips shown below are suspected Ivory-billed Woodpecker from a variety of species – oak, hickory, sweet gum, sugarberry, and honey locust. The specimen shots are with a honey locust chip from the old search area. The first few images show squirrel and Pileated woodpecker leavings for comparison.

Cavities are vexing. I’ve become convinced that there’s no bright line for distinguishing Pileated from Ivory-billed Woodpecker, notwithstanding the dimensions Cornell gave for “large” PIWO (3.5″ x 3.7″) versus “small” IBWO (4.0″ x 5.0″). The small ivorybill sample was limited to nest holes, and I’ve certainly seen plenty of oddly shaped and large holes being used by Pileated Woodpeckers. Thus, while I keep my eyes open for cavities, I don’t think there’s a reliable way to determine which species is responsible for creating or using large, irregularly shaped cavities, although extensive bark scaling on the tree may be indicator.

It has been a challenge to find cavities of any kind in our current search area, probably due in part to the high canopy. We did find a cluster of interesting cavities in what I call the northern sector in the 2014-2015 season. This cluster was in the vicinity where we’ve found an abundance of scaling over the years and where Phil and Matt made the recordings last year. Below are some of the most interesting cavities we’ve found in the two search areas. Cavities were much easier to find when we followed up on the Saucier sighting, but I’ve omitted those from this document.

In conclusion, there is an abundance of evidence suggesting that Ivory-billed Woodpeckers persist in Louisiana. It is self-evident that none of this evidence rises to the level of proof required for establishing beyond all doubt that the species has survived, but I think the case for persistence is a compelling one, without regard to evidence obtained in other areas since 2005.

Stay tuned for a more theoretical discussion of evidence, proof, and professional approaches thereto.

Thanks to Wylie Barrow, Fredrik Bryntesson, Patricia Johnson, Tommy Michot, Steve Pagans, and Phil Vanbergen for their input. Some photos by Steve Pagans and Erik Hendrickson.


Trip Report: March 7-16, 2018

Summary

We had a sustained presence, at least one person in the search area, between February 28th and March 16th (one rain day excepted). Between the 28th and the 16th, there were no possible encounters with Ivory-billed Woodpeckers either visual or auditory. We found a modest quantity of recent bark scaling and a few fresh cavities. We were able to do some preliminary surveys of nearby areas where local people have reported seeing ivorybills; we visited one of these on foot and think it is worthy of additional attention. We aimed a trail camera at a badly damaged hickory and have identified locations for deploying two more in the coming months. In my view, the lack of possible encounters this year supports the idea that the sounds heard and recorded last March came from Ivory-billed Woodpeckers.

Introduction

I’m opting not to post a day-by-day log for this trip and will instead focus on what I think were the most important observations made and insights gained from this team effort. I arrived in the area on the morning of the 7th and was able to spend the afternoon in the field. I was joined at various times by Peggy Shrum, Jay Tischendorf, Tommy Michot, Amy Warfield, Phil Vanbergen, and Geoffrey McMullan, a British birder, artist, and woodpecker enthusiast. (His drawing of Mexico’s woodpeckers is shown on p. 139 of Tim Gallagher’s Imperial Dreams). 

Matt Courtman arrived on March 15 and remained in the area after my departure. If he has anything significant to report it will be discussed in the next post.

Erik Hendrickson’s post details his time in the search area prior to my arrival.

Sounds

As noted, we did not hear anything suggestive of Ivory-billed Woodpecker. We did more stopping and listening than I have in many past trips; we also tried anthropogenic double knocks and playbacks of the calls recorded last year and of Barred Owls at various times, between early morning and early afternoon. At approximately 9:00 am on Wednesday, March 14, Tommy, Geoffrey, Peggy, and I heard several odd and unfamiliar “boom” sounds following my ADKs. We agreed that these were not woodpecker. They were repetitive; Tommy estimated they came in series of 5-6. While they had a metallic, industrial quality, they did not resemble shots or the typical industrial noises that are heard in the area – from logging or distant road construction. They did not seem distant, but when we hiked to the area from which they seemed to have originated, we didn’t find anything.

It’s always important to remember that correlation is not causation; while the sounds seemed to be coming in response to the ADKs, we surmised that the apparent association was coincidental. Whatever the source of the “booms”, it was a strange episode.

On the 15th, Phil and I heard some distant crow calls that were a little kent-like on first impression, enough for me to turn on my recorder and capture some of them, though we suspected crow and never thought they were ivorybill. You’ll hear Phil’s reaction when it became unquestionable that these were indeed crow calls.

They sound more obviously crow-like on the recording than they did to the naked ear, but I’m including them here since crows are rarely mentioned as a potential source of kent-like calls. The faint sonogram is not at all suggestive of ivorybill; only one frequency is readily discernible, at around 1300 hz.Screen Shot 2018-03-19 at 1.40.31 PM

To reiterate, the events of last March (2017) were unprecedented. We have had a couple of encounters involving multiple calls over an extended period – in March 2013 (these have higher fundamental frequencies) and one in the old search area, January 2010 that also involved apparent double knocks. But neither of these lasted nearly as long or involved as many suggestive sounds. Other potential auditory encounters have been brief. Thus, it’s reasonable to infer that the source is not a common species in the area. The calls strongly resemble known Ivory-billed Woodpecker sounds (and resemble them more closely than they do any known species). In my view, none of the proposed alternatives (Blue Jay, Wild Turkey, American Crow, Red-breasted Nuthatch) are plausible. I’m hopeful that further analysis will support this perspective.

Cavities

I found one cavity in a pine (not photographed) that seemed right in size and shape though it was old and only about 40 feet above the ground. I have not focused on pines given the paucity of records of ivorybills using them for roosting and nesting. This is probably ill-advised. The same applies to sycamores, as Erik pointed out in his trip report.

I found one intriguing and apparently recent cavity, high in a sweet gum in the area that we’ve considered to be a hot zone. Stakeouts have come up empty, and as is often the case, the cavity is too high in the tree and too subject to backlighting to merit targeting with a trail cam. This is an ongoing problem, even when the cavities are much closer to the camera, as in the “neck bird” image.

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I also spotted this unusual, large and rectangular cavity in a cypress.

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Scaling

My thoughts on scaling continue to evolve. As time goes on, the category of what I think is diagnostic for ivorybill grows narrower. I’ve become more skeptical about much of the work we’ve found, especially on sweet gums. Nevertheless, I still think that certain types of scaling may be diagnostic and more generally that an abundance of bark scaling in a given area may be an indicator of ivorybill presence.

This is a good introduction for those who are unfamiliar with my perspective on bark scaling and what I’ve hypothesized. While I’ve been refining thy hypothesis over the years, a couple of posts from 2013  are still relevant and may provide more insights, including into the underlying anatomical rationale. There’s a gestalt involved in identifying “interesting” scaling. I look at a number of factors:

  1. Tree species and associated bark characteristics (tightness, toughness, and thickness) factor in. With very rare exceptions, I only consider hardwoods. Pine bark is easily scaled.
  2. The bark must have been removed cleanly, with little or no damage to the underlying wood (targeted digs within a scaled area excepted). It’s important to distinguish between true scaling and bark removal associated with shallow excavation; many recent searchers have not recognized the distinction (some of the work shown at the second link is true scaling and some appears not to be).
  3. Condition of the tree or snag. I generally exclude wood that appears to me more than two or three years dead (following Tanner), so twigs and small branches must remain. (The cherry bark oak mentioned below is an exception, due to the chip characteristics.)
  4. Diameter of the scaled bole or limb. Bigger is better. So are boles.
  5. Size, shape, quantity, and characteristics of bark chips. Bigger and broader are better. Chips can also help in distinguishing between scaling and shallow excavations. Sapwood chips point to the latter.
  6. Extent and appearance of the scaling. Neat edges are one factor. Pileated Woodpeckers often remove thick bark in layers, and their scaling has a messy appearance. Similarity to images of known or presumed ivorybill foraging sign (as in the example below), though these are few and hard to decipher, is another consideration; large, contiguous areas stripped of bark are required.

(Thanks to Tommy Michot for suggesting that I include this list and for his editorial suggestions generally.)

I found most of the interesting scaling on the first couple of days in the field. When I arrived in the late morning, on March 7, I went to the area where the calls were recorded last March and where we’ve had the most indications of ivorybill presence in recent years. While we often find scaled pines in the uplands, this is the first time I’ve found extensive hardwood scaling  – on a number of small, recently fire-killed trees.

Because these trees are so small, the bark, while tight, is very thin and therefore easily removed. The scaling is extensive, but I don’t think Pileated Woodpecker can be ruled out. Some of the chips were substantial. The scaled trees are shown below. Two are black cherries, but I couldn’t identify the others. The trees were within approximately 100 yards of each other and no more than two hundred yards from the edge of the lower-lying hardwood habitat.

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Water levels were high; I was hoping to reach one of our trail cameras, but conditions made it impractical to do so (avoiding flooded areas would have involved at least a two hour detour). I did find some recent sweet gum scaling in the area, including on a freshly dead snag that we’d found in December. Although some of the chips were large, I don’t feel confident ruling out Pileated Woodpecker for much or all of this work.

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On March 8, Peggy, Geoffrey, Jay, Tommy and I visited the southern area, and Peggy spotted a sweet gum that Erik had photographed during his visit. There was new scaling, apparently done within the last week or so, especially on one of the larger limbs.

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More significantly, I found a hickory with extensive scaling of the kind I suspect is diagnostic for ivorybill. My initial thought was that this was a new tree, but Phil later pointed out that it was the one he’d found last year, with a number of thin bark strips (which we attributed to Pileated Woodpecker) at the base. Nevertheless, the scaling lower on the bole of this hickory appears to be more recent, and while flooding had washed away most of the new bark chips, a couple that we found around the base are more consistent with the larger chunks of bark that I suspect are indicative of ivorybill. (The very large chip in the image may not be associated with the scaling, though I suspect it was.)

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The bark on this hickory is approximately .5″ thick, and it remains very hard and tightly adhering. This is the first time I’ve found a hickory that appears to have been visited and extensively scaled at least twice, many months or even over a year apart. This was a surprise, as I’ve suspected that the life cycle of the beetles infesting the snag meant that this kind of feeding was a ‘one shot deal’. That does not appear to be the case with this tree, so some rethinking may be required.

Figuring out what animal is the first to scale these hickories is my top priority. We currently have three cameras deployed on hickories that are damaged, including one adjacent to this snag. I hope to be able to deploy two more this spring. If it turns out that Pileated Woodpeckers are responsible for the initial work, I will be persuaded there’s no way to distinguish between PIWO and IBWO work, although abundance and bark chip characteristics might still remain as possible indicators.

I remain convinced that the ivorybill has persisted and has been present in our search area, at least sporadically, but I will be disheartened if it turns out that there’s no qualitatively diagnostic feeding sign. Tanner relied heavily on feeding sign during his surveys (though he accepted reports from South Carolina where little or no sign was found) and rejected the 1970s Big Thicket reports in large part due to the absence of bark scaling.

If Pileateds are doing the initial scaling on these hickories, then Pileateds could be the source of virtually all scaling found in any part of the ivorybill’s historic range, including on live or freshly dead trees of any species. If this proves to be true, then the presence of feeding sign will be a weaker and more subjective indicator of presence.

But on a more upbeat note, we also found some scaling on a cherrybark oak. Because I’ve come to suspect that PIWOs can scale sweet gums extensively and well, other tree species are of particular interest. Though the tree was alive, the limb from which these chips were stripped was not recently dead (photographing it was impractical), with no twigs or small branches remaining. Nevertheless, the chips were large, hard, and dense. I haven’t found chips like these since 2013, and I think they are intriguing.

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On March 12, we found one more scaled sweet gum that piqued my interest. The jagged appearance and extent of scaling on the bole are suggestive of known ivorybill work, subject to the caveats provided above. There was also extensive older work higher on the trunk.IMGP5945

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Jagged scaling on 1935 Singer Tract Nest Tree. Courtesy of the Rare and Manuscript Division, Cornell University Library.

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Local Reports

We were rained out on Sunday, March 11 and took the opportunity to drive around in an area from which there have been several local reports (though I have not spoken to the people involved face-to-face and do not know them personally). Some of the upland areas are impressively restored stands of maturing longleaf pine; we did not find any stands of large hardwoods, though we did find places with numerous beaver-killed trees. I did not take any photographs.

On the morning of the 12th, I stopped to meet Jay for breakfast at one of the local hangouts, and an older man I’d talked to the year before pulled me aside and asked if I’d visited the area he’d told me about then. He specifically mentioned ivorybills and was very insistent that he’d seen them there from time to time during his hunting days (he’d stopped about a decade ago.) Last year, he’d recognized an ivorybill image on my phone but had not named the species. None of the other men in the restaurant were familiar with ivorybills, but this individual clearly knew what he was talking about.

A few years earlier, another person (a preacher and barbecue chef) told me he’d seen ivorybills in the same bottom (stating that he’d thought the ‘ones with white on the back were the males and the all black ones were the females’.

Peggy, Tommy, Jay, and I visited part of the bottom both men had identified and were impressed by the habitat, which is very similar to the primary search area. Like the main area, it appears to have been high-graded or selectively cut, so the conditions within a very narrow corridor (and one we believe to be fairly long) are near old-growth. We did not find any bark scaling during our brief visit to the area, but it definitely merits more attention. I suspect we were several miles southwest of the claimed sightings, so this may be an extensive, if narrow, strip of high quality habitat. The oak shown below (with Tommy for scale) was measured to be over 5′ in diameter, and many of the sweet gums in the area were well over 3′ DBH.

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Additional Tidbits

The woods were beautiful as spring was breaking out. Conditions changed dramatically over the course of my stay. Despite some very cold mornings (we only saw one snake), leaf out progressed rapidly. On my last day in the field, Matt and I found a loblolly pine that may be a contender for state champion; the current one is just under 5′ in diameter. I suspect the one shown below is close to that and may be taller. By the middle of the trip, wild azaleas were in bloom. And finding Red-headed Woodpecker feathers always causes my heart to skip a beat.

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I have one or two more trips planned this season and am hopeful that they will generate some new insights.

 

 


Trip Report: October 17-23, 2017

The first trip of the season was relatively uneventful, although we heard possible single and double knocks on Thursday morning and afternoon. Unusually heavy hunting activity and bad weather kept us out of the field on Saturday the 22nd and most of the Sunday the 23rd. Peggy Rardin Shrum joined me from Tuesday through Friday.  Tommy Michot was with us Tuesday, Wednesday, and Thursday, and Steve Pagans joined us Wednesday through Friday.

Tommy has been very good at encouraging us all to do more stopping and listening. My focus on looking for feeding sign has probably led me to do more walking than I should.  We’ve also started experimenting with playback of a couple of the March calls, cleaned up, amplified and looped by Phil Vanbergen and would like to offer it other searchers for their use. Feel free to email me for an MP3 if you’re unable to pull it from the site.

The amplification and cleaning up highlights the differences between many of our sounds and those recorded in the Singer Tract (though I still think the species involved is the same). Agitation and disturbance may account for the shorter, sharper sound of the John’s Bayou calls, and as has been discussed in prior posts, written descriptions of the calls, including Tanner’s, point to a good deal of variation.

We observed that playback of these calls often provoked responses from woodpeckers of all kinds at close to the same level as Barred Owl playbacks, though this was impressionistic not quantified. Crows and raptors sometimes seemed to react as well. I played around with some other sounds chosen more or less at random – Goldfinch, Blue Jay, Ring-billed Gull, Black-backed Woodpecker. None of these seemed to have much effect, though the Black-backed did appear to evoke a smaller number of woodpecker reactions.

Water levels were low enough to enable us to get into some of the less accessible areas, but the need to  deal with our trail cams prevented us from spending a lot of time exploring. There were no indications of woodpecker activity on the target trees, and we continue to have problems with camera malfunctions. Two of the four we had deployed seem to have failed since June; one of these may have been damaged by a tree fall, but both cams have the same issue – shutting down after booting up. We’re trying to identify the glitch and determine whether the cameras are reparable.

Tuesday, October 17

We visited the northern sector to check on our two northernmost camera deployments. The first of these (now discontinued) was a standing hickory with signs of insect damage. Tommy and Phil Vanbergen had changed out the batteries in August, and 64% of the charge remained. The second target is a hickory about 200 yards away that had lost its top in a spring storm and an adjoining beech that had also been damaged. Since August, a large hickory had fallen, bringing down a number of limbs from other trees in the process and perhaps damaging the camera without hitting directly. In addition, a large fallen oak limb obscured most of the trunk of the main target. We pulled the camera when we discovered the apparent malfunction. On the return hike, we headed east to a part of the area I had not previously explored and that has had little coverage.

Wednesday, October 18

On the morning of the 18th, I stopped for breakfast at the place closest to our search area.  Early on weekday mornings, it’s a hangout for law enforcement officers and older folks, as well as various people passing through on their way to work. A sheriff’s deputy and a couple of older men had been in the place on Tuesday, discussing local history. All three were familiar faces, as no doubt, I was to them.

For the first time, this particular bunch engaged me in conversation, asking whether I was hunting. I said no, I was looking for birds and taking pictures. They asked what ‘what kind of birds’, and I said woodpeckers. “What kind of woodpeckers?” “Rare ones”, I replied. They initially thought I was referring to “itty bitty ones”, Red-cockadeds, but I explained that I meant big woodpeckers. “You mean those Indian Hens” (meaning Pileated), one asked. I told them what I was looking for was similar but not the same and took the opportunity to show them pictures from my iBird Pro app.

The Deputy Sheriff and one of the men recognized the Pileated but said they’d never seen an ivorybill. The third guy pointed to the ivorybill image, and said, “I used to see them when I was hunting over on . . . but I gave up hunting seven years ago.” This is the second or third local claim I’ve heard from this area, which is several miles away from the focus of our efforts across a major highway.  It looks decent on Google Earth. While I’ve been wary of engaging in too much conversation with locals, it sometimes provides interesting intel, and this evolved organically; I didn’t reveal our location; and I hope it won’t result in too much gossip.

I met up with Tommy and Peggy, and we went to the southern sector to check on the other camera deployment (another tall hickory stub) to discover that one of the two cameras had failed in the same manner as the one at the northern location. We changed the batteries on the functioning camera and pulled the malfunctioning one. We met up with Steve, who had arrived later and followed another route, in the early afternoon and hiked out with him.

Thursday, October 19th

Peggy, Tommy, and I devoted the morning in the northern sector, exploring the less-visited eastern side. At approximately 8:35 we did a series of double knocks, which did not produce any immediate responses. We remained in place, and shortly before 9, we heard several single and double knocks from south of our location.  We were not recording at the time, and I considered them to be moderate possibles. We met up with Steve, who had been some distance north of us, about an hour later; he had heard our ADKs but not the apparent responses.

In late morning, we headed west and moved the functioning trail cam to the nearby hickory/beech blowdown. This is where Peggy, Tommy, Phil, and I had heard some knocks in June. It took a group effort, but we were able to move the large oak limb that was obstructing the view of the hickory bole. We redeployed the camera, trained on the bole. Given the season, it seems unlikely that this stub will be scaled in the next several months, but I anticipate leaving these camera traps in place for an extended period.

We stayed in this spot for lunch and did a little more exploring in the immediate vicinity before heading back toward the trailhead in the early afternoon.  At approximately 2 pm, as we were approaching the spot where the March recordings were made, we heard several ambient knocks, also moderate possibles, but were unable to generate any responses.

There was more shooting than usual in the area during this trip and there were distant industrial noises from time to time. These were all easy to distinguish from the possible SKs and DKs.

Friday, October 20th

Peggy, Steve, and I returned to the same vicinity and spent our time in the less visited eastern half, some of which was familiar to Steve. In addition to be being hard to reach, the terrain in this area is difficult, making it more difficult to explore.

We did not see or hear anything of note, although I found some suggestive older scaling on boles – one example on a sweet gum and one on the dead side of a still live hickory. I’d estimate that this work is at least a year old. The hickory work is of the kind I think may be diagnostic for ivorybill, and the sweet gum work is interesting for being on the bole and also for apparent large exit tunnels. I also find the excavation on the hickory to be of potential interest. The wood does not appear to be soft, and the digging does not look like typical Pileated Woodpecker work. In a couple of instances, Tanner mentioned how Ivory-billed Woodpecker work resembles that of the Red-bellied Woodpecker except for appearing to have been done by a larger animal. This hickory excavation may fall into that category.

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Old scaling on sweet gum bole

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Scaled hickory bole with unusual excavation

Saturday, October 21

I met Peggy at the breakfast place, which was unusually busy and filled with hunters. It became clear that I had not picked the best time to be in Louisiana, as this was a big hunting weekend. In addition, the weather forecast called for heavy rain by late morning. Peggy had a long drive ahead, and we agreed that there would be little point in going into the field. She left for home, and I opted to drive around, specifically to see if I could find any easy access point for searching in the vicinity that local people had mentioned and also to scout other nearby areas for potential. I had very limited success, getting a look at part of the bottom, which looked like it might have potential at a cursory glance.

The rains came on Saturday night and continued through Sunday morning.

Sunday, October 22

The rains kept me out of the field until noon, at which time I went to the eastern sector and and spent about three wet and unpleasant hours there. It rained sporadically, avian activity was generally low, and visibility was poor due to cloud cover. I didn’t see or hear anything of interest.

On Monday, I awoke to an email with a very detailed account of a sighting by someone I’ve known for several years. I may devote my next trip to following up on this report and to looking at areas in another part of the state. In any event, the next post will likely be the final in the series that this one has interrupted.

 


Bark: An Exegesis

Introduction:

According to Tanner, scaling bark was the Ivory-billed Woodpecker’s primary foraging strategy during breeding season in Louisiana. Tanner wrote that the ivorybill is “capable of easily scaling away heavy bark that other woodpeckers could not loosen.” (Tanner 1942). All woodpeckers in genus Campephilus have specific anatomical characteristics that enable them to forage in this specialized way (Bock and Miller 1959). Following Tanner, most post-Singer Tract search efforts have looked for feeding sign as an indicator of presence. Because Tanner’s descriptions are somewhat vague and many of the photographs showing feeding sign are poor, these efforts have tended to focus on decay state and bark adhesion without taking bark characteristics and tree species sufficiently into account. I posit that tree species and bark and wood characteristics are key factors that should be considered. I further posit that extensive bark scaling on live and recently dead hickories (genus Carya) may be beyond the physical capacity of the Pileated Woodpecker.

Discussion:

As all regular readers know, I’ve been somewhat obsessively focused on bark and bark scaling since my earliest years of ivorybill searching. The reason for this interest is simple: it’s how Tanner found ivorybills or inferred their presence when he couldn’t find them (Tanner 1942). Unfortunately, as discussed in a number of posts, Tanner’s descriptions are somewhat opaque, and most of the published images of feeding sign, including those in the monograph, are not very illuminating. Indeed, some of them are consistent with pileated work that we’ve documented. Plate 8, shown below, is a prime example. The caption reads, “Ivory-bill feeding sign on a slender limb”.

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Tanner’s Plate 8, Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

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Pileated Woodpecker feeding sign on a slender limb

Early on in my study of this subject, I hypothesized that certain kinds of bark scaling on hardwoods might be beyond the physical capacity of the Pileated Woodpecker. I still believe this to be true, a view that is supported by what we’ve documented for pileated and by numerous examples of pileated scaling from online sources. At the same time, the details of what types of work might belong in this category have shifted somewhat, especially as it has become clear that Pileated scaling can look like what’s shown in Plate 8 and that pileateds will scale bark from recently dead sweet gums.

This is not to suggest that ivorybills never scale small and medium-sized branches in a similar manner. According to Tanner they did so frequently; however, I have been focused on what may be diagnostic for ivorybill. It seems likely that there is considerable overlap between ivorybill and pileated work when smaller branches are involved (at least on sweet gums).

The sequences we obtained showing pileateds scaling a sweet gum limb have inspired me to look more deeply at the characteristics of hardwood bark and pursue some research avenues that I hadn’t considered previously. I’ve linked to some of the sources in recent posts, but I’ve had some additional insights that seem important enough to share. Every time I think I’ve run out of things to say on the subject, something new crops up.

Like virtually everyone else, I’ve followed Tanner and focused on two bark characteristics, “tightness” and thickness, but it recently struck me that other features might be important as well. And the literature, mostly from the lumber industry, supports this idea.

Tanner suspected that the Singer Tract ivorybills preferred sweet gums and Nuttall’s Oaks because the bark is thinner, and the thinner barked limbs had “more borers” than thick barked ones. While abundance of food was likely a factor, I suspect that, at least with respect to sweet gums and possibly Nuttall’s oaks, ease of scaling and access to food played a role.

It’s important to point out that in live trees, hardwood bark adhesion varies seasonally, with bark becoming tighter during dormant stages and looser (with considerably less variation from species to species) during the growing season. Bark is often if not always tighter on recently dead trees than on live ones (Stokland et al. 2012).

In addition, “The structural and chemical traits of dead wood, inherited from the traits of living trees, are also major drivers of wood decomposition and these traits vary greatly among tree species.” (Cornellisen et al. 2012). The authors of the linked paper point out that other factors, including size and site, can also contribute to the way that bark loosens post-mortem, but specific traits seem to be paramount, especially since the scaling we deem to be suggestive, whether on standing or downed wood, is on trees that are alive or are recently dead. Because the scaling has a very distinctive appearance, we also deem as suggestive hickory snags and stubs that appear to have been scaled some years ago, even if they are in a considerably later stage of decay overall. Bark attached to hard wood on these longer dead stubs and snags often remains tight for 3 or more years after death.

A 1978 report, entitled Bark and Wood Properties of Pulpwood Species as Related to Separation and Segregation of Chip/Bar Mixtures examined bark morphology and strength properties in 42 different pulpwood species and identified factors that impede the mechanical removal of bark from logs. These include: cellular structure, bark adhesion, bark strength, bark toughness, wood toughness, specific gravity/density, and moisture content. (Institute of Paper Chemistry 1978) One caveat about this report: a subsequent paper gives the sample size for each species, and in many cases (including sweet gums) it was only 2 (Einspahr et al. 1982)

It may be counterintuitive, but the authors found that shagbark hickory was far and away the most difficult bark to remove. (The tightly adhering layer is thin, beneath the dead bark that gives the species its shaggy appearance.) One key finding was that:

“Morphologically, the presence of fibers increases inner bark strength and, when sclereids (a type of cell) are present, bark strength is decreased. Inner bark strength, in turn, has a major influence on hardwood wood/bark adhesion. The multiple regression equation employing wood toughness and inner bark strength accounts for 72% of the wood/bark adhesion variation encountered.”

Sclereids are virtually absent in hickories (Nanko 1980) and a few other species that don’t approach the hickories in bark strength and bark and wood toughness (Eastern cottonwoods, yellow poplars, white ashes, and black willows). These tables are particularly illustrative:

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Shagbark hickories are the extreme outlier in this study, in terms of adhesion, as well as in terms of inner and outer bark toughness and strength; there are very few shagbarks in our search area, and we have never found scaling on one. I have been unable to find specific information about bitternut hickory bark strength or toughness, but the industry’s debarking problem applies to all species in the genus Carya due to the near absence of sclereids in conjunction with the other factors. Moreover, the industry does not differentiate among hickory species (Timber Mart South 2016). This 1996 paper is worth quoting at length in this regard (full text is not readily accessible):

The amount of published literature dealing with hickory debarking is very limited. Often it is only mentioned as an example of one of the hardest tree species to debark. One study quantified this by measuring the strength of the bark-to-wood bond of 42 hardwood species, including hickory. According to Einspahr et al., the dormant season bark-to-wood adhesion for hickory is greater than 3000 kPa, which is a tenfold difference from the growing season and nearly three times as great as the dormant season wood/bark adhesion for quaking aspen (Populous tremuloides, L.), a species considered to be extremely difficult to debark in the northern United States.

Einspahr et al. also microscopically examined the failure zone in an attempt to correlate morphological differences with bark-to-wood adhesion. For hardwoods in general, they found that during the growing season, failure occurred in the cambium or in the xylem just inside the cambial zone. Conversely, dormant-season failure occurred in the inner bark. They also found that fibers in the bark increased the inner bark strength while sclereids decreased inner bark strength. Hickory bark can contain between 15 to 20 percent fiber and contains less than 0.05 percent sclereids.

While these studies have confirmed that hickory is difficult to debark, they have not addressed possible solutions to the problem. As a result, hickory is often left behind during harvesting, reducing the total usable fiber from a given stand and, over time, increasing the percentage of the species in the hardwood resource, compounding the problem of future harvests.

When a tree dies, the bark eventually loosens and detaches naturally as the cambium decays. After felling, the cambium remains alive until it has consumed all available food or dries out. Moisture loss, while causing cambial death, initially greatly increases the strength of bark attachment because additional bonding between fibers occurs as the secondary valence bonds with water are broken (Belli 1996).

Thus, even though hickory bark adheres less tightly than sweet gum bark during the growing season, it seems likely that it’s harder to scale year round, given its much greater wood and bark strength and toughness. It is also clear from my observations that sweet gum bark loosens far more rapidly than hickory bark post mortem. Note that we have found fresh scaling on both live and recently dead hickories.

Based on specific gravity of the bark – averaging 0.72 for shagbark and 0.60 for bitternut – and bark moisture content – averaging 34% of dry weight for shagbark, and 60% for bitternut – it seems likely that bitternuts are somewhat easier to debark than shagbarks but considerably harder to debark than virtually any other tree species in our search area.

Comparing bitternut hickories to other species, most oaks have a considerably higher average moisture content in their bark (Chestnut and Southern red, including Nuttall’s oaks, are exceptions) and similar specific gravities. Sweet gum bark has an average specific gravity of 0.37 and an average moisture content of 91% of oven dry weight. (Schlaegel and Willson 1983, Miles and Smith 2009). But oaks and sweet gums have sclereids, and sweet gums and all tested oak species score far lower on bark toughness and strength than shagbark and, by inference, bitternut hickories. Sweet gums and the tested oak species are fairly similar in these regards, but I suspect that the higher density and lower moisture content in oak bark makes it harder to scale and may mean that oak bark adheres more tightly than sweet gum bark for a longer period after death.

I posit that when it comes to woodpecker scaling, dormant season bark adhesion, inner and outer bark strength, and inner and outer bark toughness are all relevant factors. We know that Pileated Woodpeckers remove sweet gum bark with some difficulty and that even on medium-sized limbs, they are not consistently able to remove bark cleanly down to the sapwood. It’s also clear that bitternut hickory bark is very difficult to remove, second only to shagbark hickory in our search area. This further reinforces my view that the work on hickories is not the work of Pileated Woodpeckers.

Click here and here for examples of the hickories that are scaled in a manner we hypothesize is diagnostic for Ivory-billed Woodpecker. Also be sure to watch this YouTube video of a Crimson-crested Woodpecker (Campephilus melanoleucus) foraging. (Thanks to Phil Vanbergen for finding the clip and the scaled hickory at the second link.) I’m reposting the link to the video here because I think it very clearly illustrates many of the characteristics we associate with Ivory-billed Woodpecker work on hickories, although the species of tree being fed on is unknown. Note the striking similarity in appearance and also that the work of the substantially smaller billed Crimson-crested is not as clean around the edges as the work we’re ascribing to ivorybills.

There were no bitternut hickories in the Singer Tract, but there were congeners – pecans and water hickories. Tanner observed ivorybills scaling on these species twice and digging once. For pileateds, there were 4 instances of digging and none of scaling, as opposed to 5 scaling and 9 digging on sweet gums. The relative abundance of water hickory and pecan at Singer was 2.7%; approximately 10% of the trees in our search area are hickories, and hickories are second only to sweet gums in terms of the number of scaled trees we’ve found. While Tanner’s is obviously a minuscule data set, it may support the hypothesis that live and recently dead Carya bark is too tough for pileateds to scale extensively, if at all.

There are a number of hardwood species found in potential ivorybill habitat that are somewhere between sweet gums and hickories in terms of how easily scaled they may be and how soon after death bark decay and loosening set in – eastern cottonwoods, black willows, water tupelos, some oak species, red maples, green ashes, honey locusts, persimmons, and elms – in these species, it seems likely that close examination of the scaling and bark chips can provide some clues.

Conclusion:

Previous Ivory-billed Woodpecker searches have focused on bark adhesion and state of decay when considering scaling as possible foraging sign. Bark morphology, dormant season adhesion, inner and bark outer strength, and inner and outer bark toughness, and wood toughness are all relevant to the ease with which bark can be scaled from live and recently dead hardwoods. Specific gravity and moisture content are also factors. Bark from trees in the genus Carya is difficult to remove industrially, and members of this genus are likely the most difficult trees to scale throughout the historic range of the ivorybill. Since Pileated Woodpeckers scale sweet gum branches with some difficulty and do not consistently remove bark down to the sapwood, it may be beyond the physical capacity of Pileated Woodpeckers to scale hickories extensively and cleanly, while leaving large pieces of bark behind. Extensive work on hickories that has a distinctive appearance may be diagnostic for ivorybills; this distinctive appearance of this scaling may also be the key to recognizing Ivory-billed Woodpecker foraging sign on other species.

Lagniappe:

This may be no more than an aside, but it may be a relevant data point. I recently observed a Pileated scaling briefly on a live 14″ DBH Norway maple in my yard near New York City. The photos show that the sap is flowing. The appearance of the scaling is exactly what I’d expect for Pileated, with strips about half an inch across. Norway maple may be a decent stand-in for sweet gum; while its bark has a higher specific gravity, 53 as opposed to 37, the moisture content of the bark is almost identical, 91% as opposed to 90%.

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References Cited:

Bock, Walter J. and Waldron Dewitt Miller, The Scansorial Foot of the Woodpeckers, with Comments on the Evolution of Perching and Climbing Feet in Birds, American Museum Novitates, #1931, 1959

Belli, Monique L., Wet storage of hickory pulpwood in the southern United States and its impact on bark removal efficiency, Forest Products Journal. Madison 46.3 (Mar 1996): 75.

Cornelissen, Johannes H.C., Ute Sass-Klaassen, Lourens Poorter, Koert van Geffen, Richard S. P. van Logtestijn,Jurgen van Hal, Leo Goudzwaard, Frank J. Sterck, René K. W. M. Klaassen, Grégoire T. Freschet, Annemieke van der Wal, Henk Eshuis, Juan Zuo, Wietse de Boer, Teun Lamers, Monique Weemstra, Vincent Cretin, Rozan Martin, Jan den Ouden, Matty P. Berg, Rien Aerts, Godefridus M. J. Mohren, and Mariet M. Hefting, Controls on Coarse Wood Decay in Temperate Tree Species: Birth of the LOGLIFE Experiment, Ambio. 2012 Jul; 41(Suppl 3): 231–245.

Einspahr, D.W, R.H VanEperen, M.L. Harder et al. Morphological and bark strength characteristics important to wood/bark adhesion in hardwoodsThe Institute of Paper Chemistry, 1982: 339-348.

Institute of Paper Chemistry, Project 3212, Bark and wood properties of pulpwood species as related to separation and segregation of chip/bark mixtures, Report 11, 1978.

Miles, Patrick D. and W. Brad Smith, Specific Gravity and Other Properties of Wood and Bark for 156 Tree Species Found in North America, United States Department of Agriculture, Forest Service. Northern Research Station, Research Note NRS-38, 2009.

Nanko, Hiroki, Bark Structure of Hardwoods Grown on Southern Pine Sites (Renewable Materials Institute series), Syracuse University Press, 1980.

Schlaegel, Bryce E. S and Regan B. Willson, Nuttall Oak Volume and Weight Tables, United States Department of Agriculture, Forest Service. Southern Research Station, Research Paper SO-l 86, 1983

Siry, Jacek, ed., Species Detail Report, Timber Mart-South, 2016

Stokland, Jogeir N., Juha Siitonen, and Bengt Gunnar Jonsson, Biodiversity in Dead Wood, Cambridge University Press, 2012

Tanner, J.T. The Ivory-billed Woodpecker,National Audubon Society, 1942.

Thanks to Fredrik Bryntesson, Steve Pagans, Chris Carlisle, and Bob Ford for their help with this post.


Trip Report December 16-21, 2016, Part 2

Part 1 of this report is here.

Patricia opted to take the day off on the 19th, so I went out on my own and covered a lot of territory. I had been thinking hard about the hickories and the fact that, in virtually all cases, we’ve seen indications that bark is removed from these trees and stubs within a very brief period or perhaps in a single visit and that other woodpeckers don’t seem to begin working heavily on these trees for extended periods, sometimes for years. Except for changes in color due to exposure to the elements, some of the scaled surfaces we associate with Ivory-billed Woodpeckers can retain their distinctive appearance for at least three years and more likely five or more.

Steve Pagans later explained that this is due in large part to hardening by compression; hickory wood is hard and dense to begin with, and when a tree or stub is leaning, the wood that’s absorbing more weight becomes even denser, harder, and more impervious to rot. Thus, on many of these trees, Pileated Woodpeckers will have worked on the rotting side, sometimes extensively, while the compressed side remains very hard and virtually untouched by woodpeckers.

I examined and marked as many of these trees as I could over the remainder of the trip. Unfortunately, we did not find any of this scaling in the 2015-2016 season. Trying to find more of it this year and trying to find a way to identify potential target trees before they’re scaled will be priorities for me.

I plan to write about this work on hickories and what I think it suggests in an upcoming post. For now, suffice it to say that these particular snags and stubs are a kind of twofer having the decayed substrate that’s preferred by Pileateds and and the hard wood that, following Tanner, is preferred or used exclusively by ivorybills. As noted elsewhere, some bark on these snags and stubs can remain tight for years, and on one of the trees I examined, it was still difficult to remove, even when it had reached a point at which some of it would crumble to powder when it was being pulled off. More importantly, the harder surfaces show modest expansion of exit tunnels and targeted digging work that appear to be associated with the initial scaling (as in the hickory on the homepage and the one in Steve’s photo at the end of this post, both of which were very freshly scaled and alive when found) and little or no other work for a period of years, even when there are signs of infestation by multiple insect species (based on the presence of exit tunnels that vary greatly in size and shape). I’ve included multiple examples, long shots and details, to illustrate.

On the 20th, Patricia, Steve, Phil, and I went to Sector 2 together. We went through the area where I recorded calls in 2013 and where we found concentrations of scaling in spring 2012 and during the 2012-13 season. There has been none since in this little patch. We found no recent looking bark scaling in the morning (as it turned out, we missed a group of three sweet gums with high branch work perhaps a quarter mile to the northeast of this area, see below.) One odd highlight was coming across a patch of forest floor with many of these beautiful ice formations that had formed around the stems of a couple of species of plant.

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At a little before noon, Steve opted to turn back; we had already covered 2.3 miles. Before we went our separate ways, we all speculated on and were baffled as to what might have damaged this sweet gum. The wounds seem to have been caused by a scrape, but there were no downed trees or tops anywhere in the immediate vicinity.

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Phil, Patricia, and I proceeded another half mile farther north, reaching a hickory stub that I found in the spring of 2013, shown below. The stub was still standing, and the areas with putative ivorybill work had lost more bark but showed no signs of further woodpecker activity. The presence of a click beetle in this 2013 photo suggests that parts of the tree were already starting to rot even then.

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We found two sweet gums with extensive scaling on large branches within 30 yards of this snag. Some of the work was recent. This is something that we’re finding repeatedly; even within clusters, the interesting feeding sign often seems to appear in tighter groupings involving two or more trees. I’ll provide a possible explanation in my next post.

We found a particularly unusual bark chip at the base of the tree on the left. While it comes from a relatively small branch, the way it was removed may be significant. Over 1/3 of the chip is cylindrical encompassing almost the entire circumference of the limb; it was not pecked off piece by piece; instead, it appears to have been loosened by several blows and then pried free. The bark is hard, suggesting it was tightly attached; it was moist and contained a good deal of frass when found. The piece is very large, approximately 13″ long and nearly 7″ in circumference.

On the return trip, we found a small group of three sweet gum snags, somewhat on the longer dead side. All three had recent to fresh scaling, and there were very large bark slabs at the bases of two of them. These slabs of bark were dense and hard, suggesting that they were tightly adhering when stripped.

We came across a massive relict cypress on the way back. It’s not the first time I’ve seen this tree, but it never fails to take my breath away.

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~7′ DBH cypress. Dec. 2016. Photo by Phil Vanbergen

On the morning of December 21st, Phil and I went to Sector 1, and Patricia and Steve went to Sector 3. We decided not to deploy a camera on the downed top we had found on the 16th. We have two functioning cameras at the moment, and it seemed more prudent to deploy them on untouched substrates. We didn’t find any new scaling or a substitute target, so we decided to head for Sector 3 where I had a couple of targets in mind.

As we were walking to the car, I got a text from Patricia saying that she and Steve had just had a possible auditory encounter. Steve is a dedicated birder with very good hearing and excellent ear-birding skills. Patricia has limited experience, but she is a retired opera singer with a good general ear. Here are their descriptions of the morning’s events.

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Steve: At about 9:10 am, Patricia and I were in the bottomland hardwood area in Sector 3. The weather was overcast and cold without any wind – very good conditions to hear bird calls. We had walked southward for about a quarter of a mile in the bottomland area when we had decided to do some DKs. Actually it was Patricia’s idea to do some DKs, and we proceeded to find a small American Holly that was the right size to cut two sticks for knocking.

Patricia: I thought it would be a good location, as I remembered Frank, Steve, Mark and I had done them at the same location a few years back. I remember the fallen tree we all sat on for lunch. Steve had sardines! And where Frank sat down at the base of a tree and started to snore. When I mentioned to Mark that Frank was sleeping, Frank retorted “I’m not asleep”

Steve: The location is one where we could see for a distance fairly well. When we started the DKs, we did not keep up with how many were done or how long we did them, but I think it was for about 10 minutes. We made an effort to keep watch for an incoming IBWO that would be responding to the DKs, but we were probably not as diligent as we could have been. At a point we had engaged in some conversation. I was sitting on a sweetgum log and Patricia standing about six feet away. My right side was facing south. Patricia was talking when all of a sudden I heard what sounded like at least two distinct calls from my right. The calls sounded like textbook calls of the IBWO – a bit like a toy horn was being blown. I know White-breasted and Red-breasted Nuthatch calls very well and what I heard did not sound like either of those birds. I immediately put up my left hand to stop Patricia from talking and pointed with my right hand toward the south. I told her what I had heard while we both strained to hear any more calls. There were no more calls. Also, we did not see the bird. It is highly likely that we did not spend enough time watching and listening for the bird after I had heard it call. It is hard to say how close the bird might have been to our location because I don’t know how far their call can be heard.

Patricia: I think I did about 10 DKs, perhaps 15-30 seconds apart. When I didn’t hear anything interesting,I joined Steve, who was about 20 yards away. We started talking, and I was responding to something he said when his hands went up and his eyes widened. He whispered, “Did you hear that? Kent calls?” I shook my head no. We listened for a while, but probably no longer than 5 minutes.

Steve suggested we do another round of DKs to see if we could call in whatever made the sound again. I asked him to do the next round, as I my hands were stinging and sore; plus I wanted to hear them from someone with more experience. I think that, should someone have an auditory encounter, another person should take their place during a second round of DKs.

I stayed where I was standing when Steve heard the kents but was facing directly south. After 3 or 4 DKs, I heard something similar in cadence, but it had a sharper, crisper quality to it (similar to recorded Campephilus double knocks). It came roughly from the southwest. By the time Steve joined me later, I had convinced myself that it was caused by the logging that we heard going on in the distance, also to the southwest. If I mentioned hearing the DK to Steve, I probably downplayed it, blaming the logging or a falling limb; the winds were very calm at the time, and I didn’t hear any similar sounds from the logging that morning.

I have not spent much time in the field and am reluctant to place too much weight on my observations. I’d much prefer the IBWO (should it be out there) land on my shoulder “Sonny Boy” style and leave behind a fine DNA sample, after I manage to take a series of selfies!

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Don’t we all . . . or at least that we could call them in like Barred Owls.

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Barred Owl, iPhone photo by Patricia Johnson

We met up with Patricia and Steve, and Phil set up the cams; one is currently aimed at a sweet gum stub we targeted last year before losing a camera to flooding. There is some fresh woodpecker work, I suspect Hairy, on the stub, so this may be a good  time to target it. The other cam is trained on both a downed sweet gum top and a longer dead snag. Both are within the area where we’ve had multiple possible encounters recently, not far from the heavy concentration of sign found last spring.

Toward the end of the day, Phil went to do an evening stakeout in sector 1; Patricia went with him, while I took Steve a little farther north to show him a couple of the hickory stubs. In this location as well, there were a couple of recently scaled sweet gums in within 20-30 yards of the older hickories, which were similarly about 20-30 yards apart. We also examined one of the hickories Steve photographed in 2013; it was alive at the time. This one had decayed somewhat more rapidly than many of the others I’ve found, but it’s at a lower elevation relative to the nearest water body.

Steve remarked that he’s never seen feeding sign like this anywhere else, and he has spent countless professional hours in bottomland hardwood forests.

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Scaled hickory, 2013. Photo by Steve Pagans.

Frank, Phil, and John Williams will be in the search area over the next few days, so there may be another report coming soon, in addition to the post I’m planning on hickories and foraging behavior.


Trip Report December 16-21, 2016, Part 1

On this trip, I was joined by Patricia Johnson (my wife) who was making her first visit to our search area in over two years. Phil Vanbergen was along on Friday, when a classmate of his, Jeremy Irion, spent also spent the day with us. Steve Pagans, retired forester at D’Arbonne National Wildlife Refuge, was very active in our efforts until he was sidelined with back trouble. He too made his first visit in over two years on Tuesday and Wednesday. It’s great to have Steve along for his birding skills and knowledge of this habitat type. Phil returned on Tuesday and Wednesday, and spent Thursday in the woods on his own. Frank Wiley was unable to get out this time around.

Prior to our departure, rain was predicted for three of our planned field days, but as it turned out, the weather was generally tolerable, if cold at times; Saturday was the only day when conditions, high winds and predicted thunderstorms, kept us away. Patricia and I took that day as an opportunity to visit Tensas National Wildlife Refuge (on the site of the Singer Tract) and Bayou Cocodrie National Wildlife Refuge. More on these visits below.

Although I didn’t have any possible encounters (Steve and Patricia’s will be discussed in Part 2), the trip was an incredibly productive one for me. We found a good deal of recent feeding sign. I also took the opportunity to look at over 10 hickories that have been scaled within the last several years. This is the type of work I think is most compelling for ivorybill.

I got what I think are some important new insights and some ideas about how whatever is stripping bark is behaving over time; these merit a separate post that will likely follow Part 2 of the trip report; I also anticipate writing an addendum to the feeding sign page I added recently. I hope these insights can inform our strategies going forward. It’s especially helpful to get fresh perspectives, so I’m grateful to Phil, Steve, and Patricia. Each in their own way helped me think a little more deeply about my observations; a conversation I had with Frank after a long day in the field was similarly helpful.

The groups of images in this post are in “tiled mosaic” format. Clicking on any single image will enable you to scroll through the group and enlarge the individual photographs if you choose to.

We met Phil on the edge of what we call Sector 1 at 6:45 am on the 16th. The weather was cloudy, cold, and windy; later in the day, the thermometer soared to nearly seventy, but the skies remained a wintry gray, less than ideal conditions for finding feeding sign or observing birds. Nevertheless we did find some recent work on both standing and downed sweetgums and on a broken hickory limb, all of this in an area where we’ve found an abundance of scaling every search season. None of this work is in the category I find most compelling; the hickory limb is probably most interesting due to the characteristics of hickory bark and the very large bark chip we found below the limb. Given what we’ve observed on hickory boles, this may be good target tree for later in the season.

The scaling on the downed limb has some features that might point toward Pileated, especially the layered appearance at the lower right and the patchiness of the work on the smaller limb. Conversely, the shredding of the cambium on the stub is consistent with what Edith Kuhn Whitehead told us her father associated with ivorybills.

Phil and I considered aiming a trail cam at the downed limbs but decided the work was not quite interesting enough.

The weather forecast for the 17th was ominous, with winds upwards of 20 mph and thunderstorms predicted for the afternoon. Patricia and I thought we might be able to spend a couple of hours in Sector 1, but when we reached the trailhead we found a truck parked where we were planning to walk in. Given the bad weather and the presence of hunters, we decided to head straight for Tensas, a pilgrimage I’d been wanting to make for some time.

The drive took a couple of hours, and our Wayz app sent us on a couple of roads that dead-ended in bean fields, but we finally made it, only to find the visitor center closed for the weekend.

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We took a walk on the boardwalk behind the headquarters and found a dead tree that had been almost completely stripped of bark, large soft slabs of which were lying around the base. I’m posting a photograph to illustrate how difficult it can be to explain what we’re finding to those who haven’t seen it firsthand. I doubt there are ivorybills in Tensas, but if I found this work in our area, I wouldn’t suspect ivorybill. The remaining adhering bark is loose and decaying; the large slabs we found on the ground were soft and pliable. The tree in the background has a little bit of scaling on it too, but it is in an advanced state of decay, and the bark has not been removed from large, contiguous areas.

As we drove around Tensas, we did note occasional instances of high branch scaling, but nothing remotely suggestive. Again I’m again including these examples in hopes of providing more clarity with regard to the kinds of feeding sign I find suggestive for ivorybill; this work doesn’t qualify; it is on very small, longer dead limbs; it does not involve large, contiguous areas; nor does it reach the bole or larger parts of the limbs.

We spent a couple of hours exploring the refuge from the road, stopping at Africa Lake, on the West side of the Tensas River, and then drove Sharkey Road, stopping for a somber moment on the bridge over John’s Bayou. I’m facing south in the picture below; Tanner would have walked north to the core of the home range. There are strips of maturing woods along the banks of the bayou but bean fields to the east and west. Tensas is big, extensively wooded, and an impressive restoration effort is under way, but the visit left me saddened, with a more visceral sense of what was lost when the Singer Tract was logged.

From Tensas, we went to Bayou Cocodrie, a nearly 15,000 acre refuge that’s part of a large, east-central Louisiana potential habitat complex. While the corridors are not uninterrupted, they encompass many thousands of acres of maturing forest, from D’Arbonne and Tensas National Wildlife Refuges to Raccourci Island and Tunica Hills. There’s some connectivity with the Atchafalaya Basin as well. Bayou Cocodrie is fairly isolated and hard to reach (Wayz was unhelpful again); it includes a small (775 acre) stand of old growth hardwoods (the Fisher Tract), and there may be a good deal more surrounding forest that’s suitable for ivorybills. I met a professional hunting guide a couple of years ago, and he claimed to have had an encounter there. We’re planning to visit Bayou Cocodrie and see the Fisher Tract and surrounding areas on my next visit.

Patricia and I were on our own on the 18th, which was a much colder, clearer day after some early morning clouds broke up. We spent the early part of the day in the northeastern part of Sector 1 and didn’t find anything of interest. We went to the scaling concentration in Sector 3 in the latter part of the morning and stayed in the area until about 3 pm.

I didn’t notice any new scaling worth mentioning, but we found a limb that had fallen and broken apart in the storms that had raged through the night before. The scaling had been done before the branch fell, and except for one targeted dig, there was no associated excavation. While some of the bark had loosened, it was tight (impossible to remove without an implement) on the edges. I’ve included several images because they help illustrate the difference between the very extensive scaling we’re finding in our area and what’s common elsewhere (as shown in some of the Tensas photos). Patricia is 5’9″.

Stay tuned for Part 2.


Feeding Sign: Further Reflections and Clarifications

I’ve created a page that expands on this post and should provide a good introduction to our thinking about the three most intriguing types of feeding sign, with images from the second and third categories. Think of this post as the shorter version.

Over the years, I have written a great deal about bark scaling and the types of work I think are diagnostic for Ivory-billed Woodpecker; however, I don’t feel that I’ve been effective enough at conveying the nuances of what I look for in situ. I’m going to try a somewhat different approach using images that have been posted previously. I will be focusing on the category of bark scaling that I think is most compelling for Ivory-billed Woodpecker. I hope that the tiled mosaic layout will make it easier to get my points across.

The scaling I find most compelling for ivorybill is on hickories, mostly or all bitternut hickories (Carya cordiformis).  This work represents a relatively small subset of the suspected ivorybill feeding sign we’ve found, as would be expected given that under 10% of trees in the area are hickories. It is not the type of foraging sign that Tanner emphasized, and I’m not suggesting that scaling on boles is the ivorybill’s predominant foraging strategy. I emphasize this work because it has a distinctive appearance, one that differs dramatically from presumed Pileated Woodpecker foraging sign on the same species.

The above images show presumed Pileated Woodpecker work on a recently dead bitternut hickory found last February. It seems reasonable to infer that this is Pileated work because of its extensiveness and the abundance of fresh chips at the base of the snag, suggesting the work was recent and was done by a large woodpecker. Some readers might be inclined to think of this as “scaling”, when in fact it is shallow excavation. The small size of the chips and the fact that some of the chips are sapwood, not bark, support this idea. Contrast the roughened appearance of the sapwood with the clean bark removal in the images below. Also contrast the extensiveness; while the work shown above involves fairly large areas, it pales in comparison to the very extensive scaling shown below.

Edited to add: I think squirrels can also be ruled out for this work due to the involvement of the sapwood, apparent bill marks, and the presence of insect tunnels.

I think that all of the images immediately above show Ivory-billed Woodpecker work, most of it fresh. The similarity in general appearance from tree to tree should be self-evident. This type of scaling can be found from within approximately one foot off the ground to the upper parts of boles. Large Cerambycid exit tunnels are visible in the sapwood. Bark chips, when found, were large, and the only hints of excavation involved targeted digging to expand the exit tunnels. It’s worth noting that the Hairy Woodpecker in the trail cam photo above spent several minutes removing a quarter-sized piece of bark. The Pileated Woodpecker also spent several minutes on the tree; it pecked and gleaned and looked around but did no excavating or scaling.

Bitternut hickory wood is “hard and durable” and the bark is hard and “much tighter than on most other hickories.” The bark is sometimes described as being thin, but this appears to apply to young trees only. On mature boles, it can be .5″ thick or more.

Due to these qualities, the decay process for hickory snags is often more gradual than for other species, especially in higher and dryer areas. This means that the wood can stay hard and the bark remain tight for as long as three years; such is the case with the tree shown in the penultimate image above. This has enabled me to do periodic checks on some of the snags, and in most instances, they have shown little or no indication of further woodpecker work for extended periods, until the wood starts to soften and excavation becomes easier. Whatever is doing this work seems to be hitting the trees once or twice without returning or, less frequently, to be making visits several months apart. I think this suggests a thinly distributed, wide-ranging species as the culprit, and in my experience, Pileated Woodpeckers tend to return to feeding trees on a regular basis.

In my view, this very specific type of work is diagnostic for ivorybill and is beyond the physical capacity of the Pileated Woodpecker. I’d suggest that similar appearing work on other tree species should be considered strongly suggestive. When it comes to the high branch work that Tanner emphasized, it is more difficult to rule out Pileated Woodpecker. As discussed in several recent posts, this type of foraging was the predominant one during breeding season and immediately after fledging young, at least for the John’s Bayou family group. Thus, for work higher on trees, where bark is thinner and tightness cannot be assessed, abundance is likely a key indicator. From this perspective, it may be significant that our friends the Carlisles who are searching in the Pascagoula area have found only two sweet gums with work that I consider to be intriguing and consistent with what’s described in the literature. By contrast, I found over 50 such trees in our area in the 2015-2016 season alone. Whether or not there are ivorybills in the Pascagoula, the difference between the Carlisles’ observations and ours is dramatic and suggests that something unusual is going on in the Project Coyote search area.

 


Old Singer Tract Images Compared with Two More Recent Ones (from Elsewhere)

1967 slides taken by Neal Wright of a putative Ivory-billed Woodpecker in Texas are viewable on Vireo (search Ivory-billed Woodpecker), but high resolution scans have not been widely circulated as far as I know. These images were not made public until after the the Arkansas “rediscovery”, more than three decades after they were obtained. Wright’s story is mentioned in Jackson (2004) “Reynard saw the photo and said that it was fuzzy but definitely of a Campephilus woodpecker.” It’s clear from the context that Jackson had not seen the images at the time of writing.

When I first encountered the Wright slides, I was skeptical, but after seeing some lesser-known Singer Tract photographs as well as other images of Campephilus woodpeckers in cavities, my opinion started to shift. After finding additional ivorybill photographs in the Cornell archives and in Tanner’s dissertation, I thought it would be worth posting some of those images along with one of Wright’s slides for the sake of comparison.

Of course, it’s up to readers to draw their own conclusions, but I think a few things are worthy of note. First, the Wright slides were taken long before the internet, at a time when the only readily available image of an ivorybill in a nest cavity was Tanner’s Plate 1, which is quite similar to Fig. 43b (below). The posture of Wright’s bird is much closer to the ones shown in the then virtually unknown and/or unpublished images, especially those from the 1938 nest. The placement of the cavity is also strikingly similar, just below a major fork. It seems highly unlikely that Wright would have been aware of obscure Singer Tract photographs.

While the image quality is too poor to be certain, there appears to be excavation similar to work found on some Singer Tract nest and roost trees to the right of the nest cavity in Wright’s slide. Again, this is a fine detail that would likely have been unknown to Wright and that would have been difficult to fabricate.

These are very poor quality images; the malar stripe seems a little too extensive, although this could easily be a function of angle and lighting. As with the Fielding Lewis photographs, which were taken several years later, I have to wonder why anyone intent on committing a hoax wouldn’t do a better job. And in the case of the Wright pictures, it would make more sense if the template for such a hoax would have been Plate 1 in Tanner, rather than photos that were unknown to all but a handful of people, most of them at a northeastern university.

Finally, I think the fact that the images were turned over to an ornithologist (George Reynard, scroll down for his obituary) but were kept confidential for so long also tends to support the idea that they’re authentic. Neal Wright may have had an agenda – a desire to protect the area where he took the picture – but the images were not used to serve that purpose.

Edited to add: This fascinating article on a recent, non-ivorybill related hoax suggests that it’s not uncommon for hoaxes to be paradoxically uneven in quality, and that hoaxers’ motives can be murky and bizarre. Nonetheless, I think that other factors point to authenticity for both the Wright and Lewis photos.

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© N. Wright/VIREO USA – Nest with adult protruding, slide mount dated 5/70 (apparently the duplication date). Poorly defined bird is apparently peering out of a cavity in the upper left of the trunk, below the fork.

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Ivorybills at Nest, John’s Bayou 1938, female’s head protruding from cavity

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Ivorybills at Nest, John’s Bayou, 1935, male’s head protruding from cavity

 

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Images from the Singer Tract and James T. Tanner’s Dissertation Courtesy of Courtesy of the Division of Rare and Manuscript Collections, Cornell University Library

 

Another item I found in Tanner’s dissertation merits comparison with one of Project Coyote’s camera trap photos, since the tree species involved are the same. Plate 7 in Tanner shows ivorybill feeding sign on honey locusts, but the reproduction in the monograph is very dark. The figure from the dissertation is much brighter, making it clearer what Tanner was attempting to show. I think the similarity to the work on our target tree, where I had a sighting a week prior to the capture, is striking.

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Courtesy of the Rare and Manuscript Division, Cornell University Libraries

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Trail cam photo with scaled tree in the foreground and suspected female Ivory-billed Woodpecker in red box, Nov. 2009

To enlarge the trail cam photo, click here.


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.