I was in the field from March 5-17; others were around before and after. Thanks to the whole team and a couple of guests for their hard work and contributions in the field this trip. We completed the swap out of recording devices in three days, which left a lot of field time afterwards. We were very fortunate in that only one unit was tampered with and only a couple malfunctioned. This is a very low rate of loss for these units.
We continue to have possible encounters in the area, perhaps at a higher rate than in past seasons, though the number of potential observers and time spent in the area has increased this year. And we have gotten some very preliminary results from the first round of deployments.
In addition to the audio deployments, we’re focused on obtaining DNA this season and have been refining the protocol for doing so. On this trip we collected samples from a couple of different forms of feeding sign, one I think is more promising than the other.
Here’s the basic protocol: collect a small quantity of material from places where a woodpecker’s tongue may have been; place it in a vial containing buffer and seal. With luck, genetic material can be obtained from these surfaces, and we can rule in or rule out ivorybill as the source of some kinds of feeding sign.
We also plan to collect samples from the most promising cavities. And are evaluating them following Cornell’s criteria. Cavities are graded:
A: very large cavity in size range of IBWO with irregular oval or rectangular shape (4.0–4.75in [10.2–12.1cm] wide and 5.0– 5.75in [12.7–14.6cm] tall);
B: cavity larger than typical PIWO cavity but shape is fairly regular, nearly perfect round or oval; or, cavity of irregular shape and within upper size range for PIWO, and lower size range for IBWO (3.5in x 3.7in or [8.8cm x 9.5cm] large PIWO and 4.0in x 5.0in [10.1cm x 12.8cm] small IBWO);
C: cavity of fairly regular shape, nearly perfect oval or round, in the upper size range for PIWO and lower size range for IBWO. Same dimensions as for B.
Here are some promising cavities (I’d grade all of them A or high B) I found last trip, plus some we know are being used by other species. I found more cavities this trip than I ever have in the past, mostly because I was paying attention. There’ll be some explanation in the captions. The truth is, no one really knows about cavities; I’ve seen a lot of variation in what PIWOs do; so a lot of this is speculation. I do think scaling or suggestive feeding sign on a tree with a cavity in it may be an indicator, including that the cavity is a former nest.
It can be a tough call. The first pair of cavities shown below is being used (and was likely excavated by) Red-bellied Woodpeckers. The size is deceptively large, but the small diameter of the high limb is an indicator.
The intriguing cavity below was being used as a PIWO roost but would probably have been graded A for its large size and irregular shape. There’s a second, possibly connected, cavity slightly higher and to the the left. Both are oddly shaped. The snag is severely decayed. But again, we have very limited information, so there’s no way to know whether IBWOs might avoid badly decayed snags.
Regarding feeding sign, extensive scaling on boles, especially of mature trees with tight bark, seems likeliest for Ivory-billed Woodpecker work. Hickories are the highest priority within this category, and we have only found a few such trees over the years. Extensively scaled sweet gums, like the one shown, are worth noting too. A second category, involving smaller sweet gums and branches, is also intriguing. Ambrosia beetles are the prey species involved in this work, which involves extensive stripping and targeted digs into the insect chambers.
In all cases, it’s important to distinguish scaling from shallow excavation with associated bark removal.
The appearance of this work is distinctive. The bark is removed cleanly, and there’s almost no damage to the underlying wood, except for expansion of the exit tunnels on the surface. We hope that DNA can be extracted from these tunnels and that the scaling shown in the first image is fresh enough to be a good candidate. Based on the life-cycle of the beetles involved, I suspect this work is likelier to be found in the latter part of spring and through summer, but keep your eyes open anyway.
We’re finding that Pileateds also feed on hickories and begin by removing bark. They go about it in a different way, however, excavating through the bark and into the sapwood. The appearance of Pileated work on hickories is similar but somewhat different. It tends to be patchier, without less extensive and contiguous bark removal. The chips are smaller, a mix of bark and sapwood, and the appearance of the wood in the areas where bark has been removed is distinctly different, as in the images below.
Extensive scaling on boles of other species is also noteworthy and may have DNA collection potential. There’s more room for overlap between what IBWO and what PIWO might be able to do, since the properties of hickory bark are unique. Look for extensiveness, large to enormous chips, and lack of damage to the underlying wood.
The final category involves sweet gum saplings and small to medium-sized limbs. I have found this distinctive appearing work in only two years, in a small cluster in 2015 and in a single example this season. The bark is extensively, indeed almost entirely, stripped. Chips on the ground should be large. Leaves should be still attached. The beetles’ brood chambers should have been vigorously attacked, and you may see superficial horizontal scratches in the sapwood (not the deeper grooves that used to be mistakenly ascribed to IBWO).
This was a longer trip than usual, and I was wiped out when I got home. We will be returning at the end of April to collect the units. This will mark the end of the deployments for this season, though we will continue to work with the trail cams, with a couple transferred to new locations. I’m hoping to have a guest post from a team member before the next trip.
I suggest reading Part 1 for background and context, if you haven’t already.
The target of this deployment (5/3-6/3/2018) was the sweet gum stub discussed here. The tree was killed when its top was blown off in spring 2015. A patch of recent scaling was found this season. I suspect the initial scaling is woodpecker work, but squirrel is also possible. The extent is modest in terms of what I hypothesize is diagnostic for Ivory-billed Woodpecker:
A particular and distinctive looking type of extensive scaling (large contiguous areas with bark removed) with associated insect tunnels on bitternut and pignut hickory boles – live trees, snags, and stubs – may be diagnostic for ivorybill. For recent work, the presence of large bark chips at the base of such trees is a related potential diagnostic.
Insect tunnels are present on this stub. Species is/are unknown, and tunnels are small compared to those found in the hickories.
In contrast to the hickory discussed in the previous post, there were no woodpecker captures over the course of this deployment and squirrels were very active on the scaled area, appearing on May 4, 5, 8, 10, 12, 13, 15, 17, and 22. There were multiple visits on some days, and the total time spent on the scaled area was significant, upwards of an hour, with at least one visit lasting nearly 25 minutes. It was surprising that squirrel activity ended on the scaled area ended on May 22nd, and there was none over the next 11 days.
Over the course of this deployment, squirrels removed a modest quantity of bark, apparently in strips, from part of the scaled area. They did this inefficiently – with some difficulty and with the grain. The bark, already softer and weaker than hickory, has weakened in death and is at best moderately tight (relatively easy to peel off by hand). Captures from the first and last full days (note the Hooded Warbler on the branch to the left) of the deployment reveal how little bark was removed, all or almost all from the right side of the scaled area. (Click on the images to enlarge them.)
This suggests that squirrels are unlikely candidates for removing bark from hickory boles in quantity, leaving large chips behind, or initiating extensive scaling on hickories. In my view, it’s probably impossible for them to do so. The results for Pileated Woodpecker from the hickory deployment and squirrel from this one support my hypothesis that Ivory-billed Woodpeckers are the source of the initial hickory scaling. But more data are needed.
Before turning to the trail cam captures and accompanying images of the scaled surfaces, I’ll provide some background information on the impetus for this post and on squirrel behavior.
An email discussion of squirrels and bark scaling was ongoing prior to my starting to review the images from this deployment. Wylie Barrow suggested an alternative explanation: that squirrels might be the source of much of the scaling (including the work on hickories) that’s taking place in the search area. He pointed out that . . . “Squirrels have removed bark from 1/4 to 1/2 of the trunk and several large branches from large oaks in my yard… and they work with great speed. They often leave large bark chips on the ground beneath the trees. Trees are living and bark is tight and fairly thick.” (W. Barrow, pers. comm.)
At first, I took some umbrage at this suggestion, thinking that I had thoroughly examined and considered what squirrels might be doing on the hardwoods in our search area and what the upper limits of their capacities might be. While my basic views on this are unchanged, and the trail cam images tend to support those views, I’m grateful to Wylie for keeping me on my toes.
It’s certainly true that in the past I have failed to consider squirrels and the role they might play in bark scaling, and this has led me down some blind alleys, as was discussed in a series of posts in early 2016. I have also been too confident in those conclusions, even though I think this material supports them. Wylie’s suggestion led me to conduct additional online research on squirrels (and he provided additional references).
I had a number of off-the-cuff theoretical and observation-based objections to Wylie’s suggestion.
One evolutionary objection is reflected in a comment I made early in our exchange: “the predator in question would have to have evolved to take advantage of this very narrow window of opportunity when the insects are near the surface . . .” I thought and still think this points toward a woodpecker as the source, and toward a Campephilus woodpecker in particular, since this foraging strategy is characteristic of the genus.
The hickory scaling is associated with sapwood dwelling Cerambycid infestation, and signs of woodpecker activity (targeted digging around exit tunnels) are present in all cases. The homepage tree was very recently scaled when found, and woodpecker evidence was present. Wylie replied that squirrels are opportunistic and might be feeding on larvae; he went on to suggest that woodpeckers following the squirrels and doing targeted digs around the exit tunnels was a possibility.
In one paper on a tropical species of squirrel, it was observed that they prefer palm nuts infested with beetle larvae. The authors also note that squirrels have a strong preference for obtaining food in the most efficient manner, and that Eastern gray and fox squirrels will choose nuts lacking an endocarp (the hard inner shell) over those that are harder to open. When confronted with an endocarp, the tropical squirrels would attack it at its weakest and thinnest point, as do Eastern gray and fox squirrels :
Two of these pores have dead ends (with 1-mm depth), and the third is the germinal pore, which is deeper but is closed by a soft and easily penetrable tissue, located on the side opposite the fruit’s internal gibbosity. The internal gibbosity is a projection of the endocarp that inhibits the squirrel’s access to the endosperm when the fruit is opened from the side containing the dead-end pores. The squirrel must determine the position of the internal gibbosity to avoid it and thus save energy and time in obtaining the endosperm. These rodents are known to identify the side without the internal gibbosity even before beginning to open the fruit, with >90 percent success (Bordignon et al. 1996, Mendes & Candido-Jr 2014). However, how the squirrel identifies the side without the internal gibbosity remains unknown. As the gibbosity is always on the side opposite the germinal pore (Bordignon et al. 1996), this pore is an important access point that the squirrel can use to open the fruit efficiently. It is believed that the squirrel manipulates the fruit by pressing the three pores with its upper incisors, using the pore without a dead end for support so that the lower incisors can open the endocarp (Bordignon et al. 1996).
Efficiency is one of the main factors that determine the foraging strategy of Sciuridae. A laboratory study conducted with the squirrels S. carolinensis and S. niger found that individuals preferred various species of nuts with low energetic value that lacked an endocarp or shell over high energy nuts with an endocarp (Smith & Follmer 1972). These results suggest that there is a high cost in energy expenditure for processing seeds with endocarps for these species.
(Alves et al. “Queen palm fruit selection and foraging techniques of squirrels in the Atlantic Forest,” Biotropica 50(2): 274–281 2018). Efficiency is an important consideration in this context, especially with respect to hickories.
The reasons squirrels strip bark are poorly understood. Pine (or red) squirrels attack a number of tree species, “[d]uring winter, spring, and early summer, bark stripping and tree girdling for consumption of phloem and cambial tissues is common (Hosley, 1928; Linzey and Linzey, 1971; Pike, 1934). Pine squirrels also eat the bark of rust galls (Salt and Roth, 1980) as well as sap from sugar maple trees (Acer saccharum) in the northeast (Hamilton, 1939; Hatt, 1929; Heinrich, 1992; Kilham, 1958; Klugh, 1927; Layne, 1954) and yellow birch (Betula alleghaniensis) in the Great Smoky Mountains (Linzey and Linzey, 1971). Widespread, systematic sugar tapping by pine squirrels occurs in New England (Heinrich, 1992).” (Steele, M. A. 1998. “Pine squirrel (Tamiasciurus hudsonicus),” Mammalian Species 586:1–9).
Red squirrels have also been observed feeding on spruce bark beetles. (Pretzlaw, et al. “Red Squirrels (Tamiascurius hudsonicus) Feeding on Spruce Bark Beetles (Dendroctonus Ruffipennis): Energetic and Ecological Implications”, Journal of Mammalogy, 87(5):909–914, 2006). This was a novel observation at the time, and the behavior appears to have been a sudden and opportunistic response to a climate change-related bark beetle outbreak that lowered cone production. Spruce bark is soft, flaky, and fairly loosely adhering, and the bark beetles spend approximately a year, the entirety of their larval life cycle, in the phloem and hence are a readily available food source for a prolonged period. Moreover, “[f]oraging for larval spruce bark beetles by red squirrels is an obvious and stereotyped behavior; squirrels situate themselves on the trunk of the tree near ground level and peel off the bark to reveal and ingest larvae.”
There seems to be less agreement as to why Eastern gray and fox squirrels strip bark. It has been suggested that a calcium deficiency might be primary driver. C.P. Nichols et al., “A novel causal mechanism for grey squirrel bark stripping: The Calcium Hypothesis,” Forest Ecology and Management 367 (2016) 12–20. Bark stripping by Eastern gray and fox squirrels seems to be more prevalent in areas where the species have been introduced, “[b]ark-stripping behaviour, reported so often in Europe (Shuttleworth et al. 2015), is extremely rare in their native range (Kenward 1989).” (Koprowski et al. “Gray not grey: The ecology of Sciurus carolinensis in their native range in North America”, posted on Researchgate.com, 2016).
While “extremely rare” is an overstatement, it does appear that bark stripping occurs more frequently in areas where gray and fox squirrels have been introduced. It is a major problem in the U.K and Europe but mostly an annoyance in the United States. It seems reasonable to infer that it is more common in suburban and residential areas than in mature bottomland hardwood forests, though Wylie points out that the discrepancy in the reporting may be due to demographic factors and that squirrel behavior in bottomland hardwood forests has been poorly studied.
Gray and fox squirrel bark stripping seems to occur most frequently on branches, and I found no images in which insect infestation of the scaled areas was apparent. In addition, the examples of extensive squirrel scaling found online in no way resemble what we’re finding on hickories. Thus far, we have found only two references to squirrels stripping bark from trees in the genus Carya, one from pecans in Georgia and one from limbs in West Texas pecan orchards, where fox squirrels have been introduced. It’s not clear what parts of the trees were involved in Georgia and whether this report also came from an orchard, but regardless, pecan bark is flaky and not criss-crossed, making it easier to scale.
While neither Wylie nor I conducted an exhaustive literature review, we found no records of gray or fox squirrels scaling bark from any bitternut or pignut hickories (Carya cordiformis and Carya glabra), be it on limbs or boles, in several Google searches. Given the extensive range of these species – most of the Eastern United States and into Canada – and the association between squirrels and oak-hickory habitats, if squirrel scaling of hickories occurred with any regularity within the natural ranges, one would expect references to be abundant in both the popular and scientific literature.
As mentioned in the previous post and implied above, I suspect that the criss-cross pattern that characterizes pignut and bitternut hickory bark is one factor that deters squirrels from removing it and may prevent them from removing it in large pieces. This relates more generally to the question of efficiency. The characteristics of hickory bark make it extremely difficult for any creature to remove. In addition to the pattern of the grain, it is literally the hardest, strongest, thickest bark in the forest. On mature boles it can be 3/4″ thick (compared to around 1/16″ for a hickory endocarp). It is tight (though less so when sap is flowing), and it retains these characteristics long after death. Bitternut hickory bark does not flake, and pignut does so infrequently and superficially.
Thus, both species are exceedingly poor candidates for stripping by squirrels, especially when sweet gums and an array of other much easier targets are available. In contrast to the hickories, the target tree in this deployment was a sweet gum, three years dead, with thinner, considerably softer, loosening bark
As I see it, all of this militates against squirrels as the original source of the hickory scaling. While this is inferential and we have yet to document whatever initiates the scaling, the data obtained thus far support the inference. Only recently have we been able to deploy enough trail cameras for a meaningful and sustained effort. Nevertheless, we have had many hours of captures since 2009, in both search areas. To my knowledge, the only prior unambiguous capture of squirrel scaling is the one from 2015; it involved a downed, immature sweet gum with thin bark, which was easy for squirrels to scale. A second clip may show a squirrel removing a very modest quantity of thin bark from a sweet gum limb that was already being scaled by Pileated Woodpeckers (second video clip at end of post), and Wylie observed a squirrel scaling a sweet gum branch (on a roadside just outside the main search area) in December 2015.
I no longer think scaling on sweet gum limbs (so heavily emphasized in Tanner) is a strong indicator of ivorybill presence, at least not on its own, although what we’ve found in the search area seems to be unusual. Abundance, lack of correlation with low mast years, bark chips, absence of incisor marks, and indications of woodpecker activity, especially targeted digging, may all be suggestive. Sweet gums, which are very attractive to beavers, are likely one of the most desirable targets for squirrels as well, for reasons of flavor and efficiency.
But we have documented no squirrel scaling on hickories, live or dead, on limbs or on boles, partially scaled or with bark intact.
I think the results from this deployment shed considerable light on the issue of squirrels and bark scaling, especially what they do (or can do?) on a mature bole with thick bark. So let’s go to the videotape, as a New York sportscaster used to yell.
Squirrels on a Sweet Gum Bole
As with the previous post, our Plotwatcher Pro trail cam is programmed to capture one image every twenty seconds, and these time-lapse sequences have been converted into QuickTime movie format. If you want to get a clearer sense of how the squirrels are behaving, you can step through the films frame-by-frame. If you elect to watch just one of the clips, the one from May 8 that starts at Frame 1500 (the squirrel spent 24 minutes on the scaled surface) or the one from May 12 that starts at Frame 1574 might be your best bets. Discussion and close-ups of the scaled surface follows the bonus imagery.
While we had no woodpecker detections on the stub and bird captures were few, we did catch some hogs (piglets?) and a beaver. Also captured but not shown were a Northern Cardinal and an Eastern Phoebe.
Discussion and Details
As best I can tell, the only expansion of the scaled area involved a narrow strip at the upper right, probably no more than 12″ x 2″, and a little widening at the very top, although this was an area where the squirrels spent a considerable amount of time.
Let’s look at some details from that scaled area.
While there appears to have been some woodpecker excavation at the middle left of the larger scaled patch, there’s no readily apparent sign that woodpeckers have been after the insects that are feeding in the sapwood. Nor is there any strong indication that squirrels were feeding on insects over the course of this deployment, though it’s possible they took advantage of snails and beetles, like the ones in the photo, or slugs, which I also saw on the scaled patch.
The edges of the bark shown in the close-ups, especially the one at the top, show signs of having been gnawed, although this is subtle, and sometimes impractical as an identifier, since such close examination is not always possible in the field. I presume that the abundant squiggly abrasions to the surface of the underlying wood are incisor marks, something we have not observed with other scaling we’ve found.
With regard to what was left behind, the first three photos show what I found at the base of the snag when I discovered the scaling on May 1, 2018.
The large, though narrow, strip of bark was the biggest one I found at the base and is one of the main reasons I suspect that woodpeckers initiated the scaling with squirrels following, although I would not rule squirrel out completely. In any event, the bark was so soft and weak that it broke in my hand when I picked it up on June 11. The other thin strips are more consistent with what I’d expect for squirrel, and the tiny orange pieces of cambium are a giveaway.
The situation had changed little during this most recent trip. The picture with my boot shows the larger pieces of bark I found at the base, including the one shown above after it broke. They may be consistent with woodpecker (possibly including Red-bellied or Hairy), but I suspect that both squirrels and woodpeckers were involved in the bark removal.
Edited to add: For any extensive squirrel work on mature boles, especially hickories, I would expect to find many small pieces of bark on the ground, similar to those shown above, as in this dramatic example.
My main objective in targeting this stub was to observe it over time, more for what might happen as the decay advanced and whether it might become a target for ivorybills; it’s the type of “stump” that Pearson described as being favored by ivorybills after his visit to the Singer Tract in 1932, though Pearson’s “stump” (scroll down in the linked article) was much longer dead. The bark scaling, while interesting, was in the “could have been anything” category. Getting this data on squirrels was a pleasant surprise, one that I should have anticipated based on the small bits of cambium on the ground. My bias came into play, as I ascribed them to a smaller woodpecker. Between Wylie and the trail cam results, I’ve learned a lesson. In terms of the bigger picture, however, the results so far suggest that squirrels are not the source of the putative Ivory-billed Woodpecker scaling on hickories.
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.
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.
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.
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.
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.
I also spotted this unusual, large and rectangular cavity in a cypress.
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:
- 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.
- 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).
- 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.)
- Diameter of the scaled bole or limb. Bigger is better. So are boles.
- 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.
- 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.
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.
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.
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.)
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.
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.
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.
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.
I have one or two more trips planned this season and am hopeful that they will generate some new insights.
I was very pleased that we were able to have searchers in the field almost without interruption for over three key weeks in February and March. Erik was in the area alone from February 28-March 6, and conditions were good enough for him to get out for part of almost every day. At present, Matt Courtman is still in the field. I will be posting my trip report within the next few days; it covers the afternoon of March 7 through the morning of the 16th. There have been no possible encounters during this period, a stark contrast with this time last year. I’ll be addressing this in my report, but in the meantime, here’s Erik’s. It was a pleasure to read. I’ve made a couple of side comments in italics.
Back in the early 2000’s, I often used the holiday break as a time to take off from work and go birding someplace I’d never been before. Following the Ivorybill rediscovery announcement in May 2005, I decided to go to Arkansas “on a lark” and at least see the habitat where the bird had been found. There would be birding opportunities – a chance to see wintering species not present at my home in Montana, and I wanted to visit Little Rock High School National Historic Site.
After several days of birding, I saw the ivorybill. Like many other sightings, it was a brief look, but I saw the bird through binoculars, sharply focused, in good light. I made 4 more trips to Arkansas and Florida in the next two years, before my job took me to Alaska for 8 years. I made no more trips to the southeastern United States in that time.
But retirement in March of 2017 allowed me time to think about a return; and Mark graciously responded to my inquiry with an invitation to join his search effort in December 2017 / January 2018. I got to accompany him and Steve Pagans again in February; and Mark had another search planned for March, but the timing and logistics didn’t quite work out. With trepidation, I asked about searching the week before the main search effort, and Mark was encouraging. I’d seen how well Mark navigated the woods he knows so well, and Steve was equally competent (Steve is considerably more competent) – and always had his GPS available to ensure we could get out of the woods. But on my two initial trips; I often did not know where we were headed and often got turned around. I didn’t say so, but I knew I’d have to get a lot better at reading my GPS.
Mark also encouraged me to purchase a dedicated audio recorder, in case I heard double knocks or kent calls as other searchers have in the past. This was perhaps the most obvious advantage to being in the woods in March: the likelihood that ivorybills would be more vocal and/or more noticeable if they engaged in courtship, cavity construction, brooding and interaction at a cavity, or feeding of nestlings/fledglings. If I could be in the woods a week before Mark’s major search effort, then at least I was providing some additional coverage for a possible encounter.
A friend of mine said with encouragement “I’m sure you’ll see it this time!” I didn’t respond that “I don’t think so…”. Of course I’m optimistic, but my primary goal in the field is to contribute quality hours to searching for a species which has a very low encounter rate. The more hours searchers rack up, the more encounters we have. It’s important to me to contribute by adding up those good hours.
Logistics are a major part of the search effort: traveling from my home in Colorado; arranging airflight, rental car and lodging. Being prepared with the right clothing, rain gear, hat, camera, GPS, audio recorder, first aid kit, and all the miscellaneous supplies carried each day. I studied maps so that I wouldn’t be as lost as I was on my first trips. I could check online for the weather forecast and sunrise/sunset times. And then on my travel day, it takes about 12 hours from my house to my destination. I pick up lunch supplies at a local supermarket, and get ready for 7 days of searching.
It’s exciting first thing in the morning – arriving at the start point, and getting everything ready to walk into the woods. I only forgot to record the location of my vehicle once – but remembered within a 1/2 mile of my start, and that was close enough to ensure I could get out in the afternoon. I start out listening to and trying to see every bird – they’re all different from the birds back in Colorado, and if I’m standing still trying to pull a Yellow-eyed Vireo out of the shrubs – well, I can be listening for ivorybills at the same time.
Much of my time in the bottomland forests, I’m simply acting as a roving Audio Recording Unit. Although I rely on my eyes more than my ears – and at times it seems that I can see a lot of the habitat around me – I know from experience that I can’t really see all that much. Woodpeckers cling to the backside of trunks and branches. Sometimes I watch them up high, and then they move around to the opposite side of a branch – and they’re completely invisible to me. Had I not seen them move to that location, I’d never know they were there.
So as I scan the forest around me, I’m aware that there’s really only a limited amount of “space” – of “volume” – that I can peer into to check for birds. My best method for detecting the presence of many (most?) birds, is being able to hear them. So I wander around the forest, always listening, and hoping to hear a bird that may not vocalize very often.
I know from experience that I have good hearing, in the sense that I can detect very low levels of sound; often I can hear levels of sound lower in volume than my birding companions (but, sometimes others hear sounds that I miss). However, I’ve also learned that I don’t have a “discriminating” ear, and I easily confuse all kinds of species: Pileated Woodpecker sounds a lot like Northern Flicker; Northern Cardinal sounds a lot like Carolina Wren; Tufted Titmouse can sound like Carolina Chickadee. It always makes sense to me when someone tells me what I’m hearing, and often – given enough time (if the bird continues to call) – I can figure it out. But I know I’m not as good at identifying birds by sound as I am by sight.
I’m pretty good at identifying birds in the field and in photographs. Often, I only need a few pixels to correctly identify a bird. I make my share of mistakes, and often call out the name of a bird before I’ve completely processed all the information – and my initial identification (part of the thought process for arriving at a final ID) is incorrect. But while I make lots of mistakes while trying to arrive at the conclusive ID for a bird, I’ve got to be certain in the end. Entire books have been written on this topic – and that makes sense to me.
Searching for ivorybills is very different (for me) from “birding”. Birding is a fun, enjoyable activity that I do regularly, in all kinds of habitats, with lots and lots of opportunities to see and identify birds. Searching for ivorybills is mostly just putting in hours without seeing or hearing anything. But my approach to searching is to go “birding” and enjoy the birds I see, and to be aware of the environs around me as I’m looking for or looking at, birds. I stop and pause for several minutes at a time. I’m not in any hurry – I don’t have to be anywhere else. I think about all the other recent encounters that have been described: someone in the right habitat, often engaged in an activity other than searching – and while relaxing, or while sitting down, or while engaged in something other that “actively looking”, suddenly they become aware of a bird that they focus on, and it turns out to be an ivorybill. I think about lots of things written about ivorybills, things that I can remember and things that I’ve heard other searchers and other birders talk about. And… I wander around the bottomland forest – listening and looking.
I made a point of looking for large cavities, and I found 8 on this trip that were large enough and asymmetrical enough for me to stop and record them. I photographed each cavity (several photos, at successive zoom ranges) and marked its GPS coordinates. I tend to consider cavities that are too small (suitable for Pileated Woodpeckers – or even smaller species), but I think I’d rather be conservative in this regard. I’d thought perhaps that if I found one or more candidate cavities, I would try to watch them as early in the morning or as late in the afternoon as I could. But I realized that simply finding the cavities, and trying to find efficient routes from the cavities to/from my vehicle, would take more time than was available to me. A fresh, or routinely occupied cavity, might be distinctive in a way that would set it apart from other cavities – and none of the ones I found was notable in that regard. If I had unlimited time, I thought about aiming a trail-cam at the “better” cavities I found – and I might give that idea more thought in the future. (The last two intriguing cavities I’ve found were not good candidates for camera traps; height, backlighting, intervening vegetation can all be problems. This issue is under- appreciated, and it became more apparent to me last trip. More on that in my report.)
I looked for scaled bark, trying to pay attention to the details Mark has taught me in the field. As a long time reader of the Project Coyote blog, I read many of Mark’s descriptions of scaling, and looked at his photographs. But having him explain scaling in the field, spending several minutes at a tree with fresh scaling, increased my understanding by at least two orders of magnitude. Mark brought to life the importance of scaling as evidence for ivorybills occupying or using the area. But I also learned that Mark has an eye for “seeing” scaling, and in my previous trips I never spotted “good” scaling before Mark did. (It’s just a matter of practice.) On this trip, I did see some tree top scaling in a sweet gum, and I saw a few downed logs (recently downed) with scaling that might have been done by ivorybills (but which also could have been done by other species). I was conscious that I tried harder looking for scaling at some times, and less hard at other times – it’s a skill that needs to be learned, and I’m still at the bottom of the learning curve.
I saw many Pileated Woodpeckers over the week, and on the first day, I noted that I saw 4 pileateds while I was standing in one spot, more or less simultaneously.
Great Blue Herons (and other species) always seemed to be aware of me, when I was walking (even walking slowly/quietly), long before I was aware of them. By contrast, when I was standing or sitting still (especially when in a shadow, but even when in the sun), birds and other animals would sometimes approach quite close, and go on about whatever they were doing, clearly not yet aware that I was present. And sometimes, even once they became aware I was present, their behavior was still reserved and they lingered at closer range than the birds (or pigs, or deer, etc.) that became aware of me as I was walking.
Some observations under the latter conditions come to mind: (1) After a large limb broke off from a tree, crashing to the ground with an impressive disruption of the quiet, two pileateds flew to a cypress tree near where I was standing quietly. The first pileated flew to the top of the cypress and drummed a couple of times. The second pileated flew to the trunk of the cypress to investigate one of two cavities, one right above the other. The pileated stuck its bill and just a bit of its head into the cavity when suddenly a gray squirrel exploded from the cavity, driving the pileated away. The squirrel clung to the cypress just a foot or so from the cavity, chattering loudly for a few seconds before retreating back into the cavity.
(2) I was sitting with my back against a birch tree, watching a fresh, asymmetrical (but small) cavity in a cypress tree across a creek (mostly taking a break in the heat of the afternoon), when a Hermit Thrush approached from a nearby shrub. The thrush moved closer (to within perhaps 15′), then off to my right, and then back in front of me, before finally moving slowly off and out of view.
(3) Eating lunch on a log one day, a Yellow-bellied Sapsucker suddenly appeared in my peripheral vision, seeming to fly right at my head, before veering off at the last second to perch on a large trunk about 12′ from me. I’d been sitting quietly (the bird might have thought I was a stump?), but seemed to recognize I was not part of the landscape when it veered off to perch and start tending its sap wells. I was able to grab my camera and take a couple photos while it was at close range, the bird never flushing as when they are startled, but rather simply moving gradually higher up the tree and out of view.
A couple of random thoughts based on my field notes: I flushed wood ducks about 3 or 4 times, and always thought it would be impossible to confuse a Wood Duck for an ivorybill. Even one time when I noted that “the ID was a little tricky”; the situation was that I wondered for a split second “what was that?”, and not “could that have been an ivorybill?”. I observed two (rather small, I think) Cottonmouths; both were well behaved and non-aggressive. Very beautiful snakes.
And one other observation: while standing quietly in a shadow, I saw a large bird, darkish in color, mostly obsucred by a tangle of vines, fly in to a log on the ground. I could not see the bird, and thought it was on the opposite side of the log from me, and there was much undergrowth that made visibility difficult. I heard several loud (very loud) raps, interpaced with quiet, and based on my time in the woods, I thought pretty sure this was a large woodpecker, foraging on a downed log, and occasionly delivering 3 to 6 heavy blows to the wood. The bird continued foraging in this manner, with several sequences of loud knocks, and I finally decided to move to my left to try to get a better angle on the log. I heard another couple sequences of raps and then quiet, and I was pleased I hadn’t started the bird and caused it to flush. I moved to my left, and a little closer to the log, and then there was a downed tree blocking my path, and some water, and I had to make some noise to get around the obstacle, and continue moving to try to see the area around the downed log better.
By this time, it was clear that I had flushed the bird, and did not see or hear it any more. I’ve thought about this event, and it emphasizes to me that birds may often be close enough to see, but impossible to see because of vegetatation blocking the view, and that birds we often think of being “in the shrubs” or higher “in the trees” are often on or near the ground. If I had to guess, the bird was either a Pileated Woodpecker or a Northern Flicker. I’ll never know.
I started writing this note with the intention of providing a simple summary of my observations during the week I was in Louisiana, but quickly realized I was describing a more general sense of purpose and the idea that looking for ivorybills is distinctly different from looking for other birds. I could add some good search hours to the effort – that was worthwhile and enjoyable to me, and although I’m uncertain how my hours contribute to the Project Coyote overall effort, I am very pleased to be part of the team.
photos follow . . .
From January 25-30, Stephen Pagans and Erik Hendrickson and I searched in the vicinity of Joseph Saucier’s October sighting. I’ll begin with a day-by-day log accompanied by some photographs, followed by a discussion of our observations and what they may imply, with photographs from our last day in the field. I’ll end with some or Erik’s photos. They help convey the experience of being in the field more effectively than most of mine. This is an image heavy post, so I hope you’ll take the time to look at and enjoy the pictures.
We had no possible sightings or auditory encounters and devoted most of our time to surveying. We did a few ADK series, sometimes followed by Erik’s tooting on a baritone sax mouthpiece, the best imitation of the Singer Tract kents I’ve heard.
There were no apparent responses. Scaling consistent with what’s described for ivorybill was abundant in most areas visited. Large and possibly suggestive cavities were also relatively easy to find. This contrasts with the primary search area, where cavities of any size are difficult to locate. This may be due to the ~30% lower canopy at this location.
We covered between 4 and 5 miles most days. For the most part, we tried to avoid repeating the same tracks. We saw substantial flocks of Rusty Blackbirds on a couple of occasions. We didn’t encounter many mammals – an armadillo, a rabbit, and some glimpses of hogs. We found little beaver sign but didn’t get into the area where we understand beavers are most abundant.
We spent the 25th and 26th in the immediate vicinity of the sighting. The habitat in this area is extensive and impressive, as it was in most places we visited. We found considerably more scaling on this trip than on the last one, as well as more cavities. As mentioned previously, the cypress in this area was not heavily logged, so many large trees remain, not all of them as obviously undesirable as the ones shown.
Suggestive Scaling and Cavities Found January 25 and 26, 2018. Scaled tree species include sweet gum, honey locust, and sugarberry.
The 27th was a rainout. We spent that morning birding from the road around a nearby lake. I went to Alexandria for a brief visit to the annual meeting of the Louisiana Ornithological Society.
On the 28th, which was cloudy and drizzly, we went to a different nearby location. Again, we found some decent or better habitat, a good deal of bark scaling, and other indications of woodpecker activity, including a cavity resembling an ivorybill roost in an unpublished image from the Singer Tract. By late morning, we reached an area of much younger forest, so we turned back.
One of the cavities strongly resembled one of Tanner’s unpublished images of an ivorybill roost.
On the 29th, we visited a different area, also nearby. The habitat was again impressive, but we only found one recently and extensively scaled sweet gum with very large chips at the base and an unusual bit of excavation on the edge of a scaled part of the trunk. An area that we could not reach appeared to contain even more mature forest and probably merits a visit in future.
On the 30th, we found another entry point. About two miles into the woods, we found more sweet gum scaling than I’ve seen in a single day, approaching or surpassing the quantity found during the most productive weeks in our main search area. Again, we found a number of potentially interesting cavities, new and old, including one in a cottonwood snag that had been extensively stripped of bark, this along the edge of an old logging road. We guessed that this concentration of scaling was in a patch of around 100 acres, but we were unable to explore it fully, so we can’t be sure how extensive it might be.
With the passage of time, I’m even more struck by the extraordinary nature of what we found on the 30th.
Some Comments on the Scaling and Cavities
As noted, I was impressed by the abundance of scaling found in the vicinity of the sighting and even more so in the concentration found on the 30th. The latter was truly unprecedented in my experience. As was the case in Tanner’s day, sweet gums with dying crowns are the primary target. The work found is consistent with that shown and described by Tanner. More on sweet gums below.
Additional work was found on honey locust, sugarberry, American elm, and cottonwood. Bark on all of these species (possibly excluding cottonwood which has high adhesion values and bark strength) becomes easy to remove fairly rapidly after death, and none of the scaling approached what I’d consider possibly diagnostic for ivorybill (again perhaps excluding the cottonwood). Still, the quantity of it may be significant.
We found no scaling on oaks. (The same has been true in the main search area, except in 2012-2013.) Steve suggested this may be due to the fact that the forest is relatively young, so the oaks are still healthy.
The sweet gum scaling was mostly found in clusters, with the notable exception of the single tree found on the 29th. This may be due to the pattern of sweet gum die-off, but we did visit areas with unscaled, dead and dying gums.
The sweet gum scaling ranged from old to very fresh, probably a year or two to a day or two. All trees were recently dead, with twigs and sometimes gum balls and leaves attached. Much of it was extensive, involving larger limbs and sometimes main trunks. Bark chips ranged from very small and consistent with what I’d expect for PIWO, to larger strips that I’ve also tended to ascribe to PIWO, to much larger chunks that I think are considerably less likely to be Pileated.
Regarding the sweet gum scaling in general, I have only found a similar quantity and quality of scaling on this species in our main search area and at this location. Scaling in the old Project Coyote search area was on a wider variety of species, with only a little on sweet gums. I never saw anything like this in over two weeks in Congaree or in briefer visits to other areas. The Carlisles, who are searching in the Pascagoula area, have found at most a similar looking example or two over several seasons, and Paul McCaslin, one of the earliest Project Coyote team members recently sent me a note reading: “I am still amazed, every time, at the scaling pics you send from the tops of those sweetgum trees. I am an ISA Certified Arborist and spend a lot of time looking up at trees and I NEVER see anything even close up on my neck of the woods.”
To cut to the chase – if Ivory-billed Woodpeckers are not present and this work is being done by Pileateds, then I don’t think either quantity or apparent quality of bark scaling on sweet gums can be treated as a reliable indicator of ivorybill presence.
With regard to other tree species, I still think that the work on hickories found in the main search area is likely diagnostic. Work on live or very recently dead honey locusts (like the one in some of the old trail cam photos), cottonwoods, sugarberries (one example found in in the old search area) and oaks (one or two examples found in the old search area and several found in the new one in 2012-2013) may be as well. Though I’ve grown increasingly cautious about sweet gums, the concepts discussed in the post entitled Bark: An Exegesis still hold.
Some Closing Thoughts
Though I have now spent multiple days in this area without any possible ivorybill contacts, I remain very impressed by the habitat and continue to think the initial report is highly credible. The scaling is abundant and suggestive, as are the cavities. However, the extensiveness is daunting, and I don’t see a way for a small, self-funded group to search it effectively. In the current search area, we have the benefits of compactness and known, readily accessible locations where there have been frequent possible contacts over a period of years. I think there’s a good possibility that ivorybills are present in the vicinity of Joseph’s sighting, and there’s sufficient habitat to make detection very difficult. I’m at a loss as to how to find them (without an infusion of J.J. Kuhn’s skills as a ‘woodsman’), if indeed any are there.
Here are some of Erik’s photos for your enjoyment.
I returned to the main Project Coyote search area where I spent December 27-January 1. I was joined by two new team members – Erik Hendrickson, an excellent birder and retired National Park Service engineer who had an ivorybill sighting in Arkansas back in 2005, and Jay Tischendorf, a veterinarian with a long and adventure-filled background as a field biologist. Erik lives in Colorado, so he may not be able to visit often, but Jay is much closer. I hope that both of them will be able to return and bring their considerable skills to the effort.
Stephen Pagans, who has been with Project Coyote since 2012, was in the area for the duration. Steve is a retired forester, avid birder with a great ear, and an outstanding photographer. This portrait of a feral hog (more on hogs later), which I think is award-worthy, is just one example of his work.
Tom Foti made it down from Arkansas for a day. Spending time in the woods with Tom, whose knowledge of bottomland forests is second to none, is always an education. On this trip, Tom pointed out that I’d been mistaken about the hickories in the search area. I believed that they were all bitternut hickories (Carya cordiformis), except for a very few shagbarks (Carya ovata), but it turns out that many, perhaps the majority, are in fact pignut hickories (Carya glabra). One of these, shown below, has a DBH of 42″ and may be a state champion. Tom also identified a nutmeg hickory (Carya myristicaeformis), an uncommon species that may not have been previously recorded in the parish.
Having such great companions for the week caused me to look back at the past year, with its terrible low points – the losses of Frank and Bill Pulliam – and high points, particularly the March recordings, which I think are among the strongest evidence of ivorybill persistence obtained to date, and to appreciate my friends, collaborators, and outside advisors. Although I’ve been the public face of Project Coyote for years (Frank wanted it that way), this has always been a team effort, although the composition of the group has shifted over time. While it would be cumbersome to name everyone involved and some frequent advisers prefer to remain anonymous, there are several, in addition to those mentioned above, whom I’d like to acknowledge publicly.
On more than one occasion over the years, Bob Ford has lifted my spirits when they most needed lifting. When I talked to Bob shortly before Frank’s death, I was despondent. I knew Frank’s prognosis was not good and was having doubts about carrying on. Bob helped me see a way forward, reminding me that the search area is important, ivorybills or no ivorybills, and that I’d done meaningful work related to its ecology in general.
Matt Courtman, who had some involvement early on and had known Frank for several years, reached out shortly after Frank died, giving me much needed moral and intellectual support and breathing new life into Project Coyote. In one of those odd coincidences, Matt’s New York relatives knew and did business with my father decades ago.
Philip Vanbergen, the youngest among us, had the presence of mind to turn on his recording device on March 11 and capture a couple of calls, setting the stage for his and Matt’s return on the 15th when the much longer recordings were made. Phil has also been responsible for our trail cams since 2016. His energy, enthusiasm, and interest in the natural history of the area are invaluable.
Peggy Shrum’s ideas, background studying raptors in the Peruvian rainforest (a considerably more challenging environment), and familiarity with tropical Campephilus double knocks are great assets. Peggy has made the long trip from South Carolina to participate several times, and it’s always a pleasure to have her along.
Tommy Michot and Wylie Barrow from Lafayette have also been great sources of support. Though Tommy is a retired biologist with a Ph.D, I admire his youthful enthusiasm, open-mindedness, enjoyment of the woods, and his sense of humor. To top it off, he’s also an accomplished traditional Cajun musician from an illustrious musical family. Wylie and Tommy have known each other for years, and while Wylie has seldom been able to make it into the field, his careful, scientific approach and probing questions help keep me on track. While I skipped it on this most recent trip, the lunches I have with Wylie and Tommy (and sometimes Phil) in Lafayette on the way home invariably help me absorb and evaluate whatever I’ve observed or experienced while searching.
Professor Fredrik Bryntesson has been a great online friend and supporter. He has shared details from his research into some arcane aspects of ivorybill history, some of which have found their way onto the blog. I hope we get to meet in person and that he will be able to visit our search area sometime soon.
Finally, Patricia Johnson, my wife – Patricia comes along from time to time, holds down the house when she stays at home. Her moral and morale support sustain me.
Though 2017 was difficult, I’m grateful to be surrounded by such great collaborators. I’m hoping for more highs and fewer lows in the year ahead . . . Without further ado, here’s the trip report. As with the previous one, I’ve opted not to do a day-by-day log. There’s not all that much to report.
The weather this trip ranged from cloudy, dreary, and damp to bitterly cold; there was little sunshine, except on January 1st, and avian activity was generally low throughout. Woodpeckers, except for Red-headeds, were mostly quieter and less active than usual. Nevertheless, on at least one day, we saw or heard all seven species (ivorybill excluded) that are found in the area at this time of year.
Birds may not have been very active, but the hogs certainly were. We saw upwards of 15-20 on a couple of days, and signs of their rooting were everywhere. Their numbers seem to have increased considerably since 2012, despite the presence of at least a few dedicated hunters in the area. We ran across these newborn hogs and assumed their mother had been shot. Their cute appearance belies their destructive potential should they survive.
We did not have any possible ivorybill encounters and found little recent bark scaling, except on two or three sweet gums, some extensive work on a pine, and a small patch on a cypress. Some commentary below the images.
Phil solved the problem with the trail cams, and we now have three deployed on hickories – two that have lost their tops and one that is in obvious decline. We’ll deploy the fourth in the spring when it will be easier to locate unhealthy trees. Given what we’ve observed and the life cycle of the beetles involved, I think scaling on hickories is most likely to take place between mid to late spring and fall.
Fresh scaling on the bole and branches of a recently uprooted sweet gum. Some of the bark chips were large and consistent with what I would expect for Ivory-billed Woodpecker.
With regard to the sweet gum scaling, it is far and away the most abundant form of this work we’ve found, and this has been true year after year. It is considerably more common in the Project Coyote search area than in other places I’ve visited or than in the Pascagoula, based on the Carlisles’ efforts there. It also matches the work described by Tanner as being typical of ivorybill, but as discussed in my post entitled Bark: An Exegesis, sweet gum bark is relatively easy to scale, making it more difficult to exclude Pileated Woodpecker. As an aside, I’m puzzled by the fact that we found a good deal of scaling on oaks in 2012-2013 and have seen virtually none since then.
While I’ve written previously that I think pine has no potential for being a diagnostic because it is easily scaled, the example above impressed me for its extensiveness and the fact that the presence of needles suggests the tree died very recently. Lighting conditions in the field were so poor that it was impossible to see that scattered patches of bark remained. This only became apparent when I brightened the photographs. Even so, the extensiveness so soon after death remains impressive.
I’ve included the beaver-killed cypress scaling here not because I think it’s likely ivorybill work; it could be, but the bark was loose, and the scaled area, while contiguous, covered only a modest percentage of the bole. What may be significant is the presence of insect work of a kind that is suggestive of suitable ivorybill prey. Tanner thought that cypress-tupelo swamps were poor habitats for the ivorybill, presumably because both are long-lived and relatively insect-resistant species and perhaps because he rarely ran across large scale deadenings of those species. The example shown here leads me to wonder about this assumption, particularly in places where beavers are present or other disturbances occur; fire, to which water tupelos are apparently vulnerable, for example. While Allen and Kellogg reported that Florida ivorybills nested in cypress and fed nearby on fire damaged pines, I think it’s possible that food sources would be sufficient in cypress-tupelo swamps under certain conditions. This relates, at least indirectly, to issues that have been addressed in the “Bits and Pieces” series. Stay tuned for the final installment.
On October 22nd, I received an email reporting a recent ivorybill sighting in eastern Louisiana. I found the report convincing for its high level of detail and decided to devote my next trip to following up on it. The source was Joseph Tyler Saucier, a pastor, avid hunter, and Louisiana native whom I’ve known virtually since early 2014, when he wrote and expressed his interest in Project Coyote. We exchanged a few emails at that time, but he was in more frequent contact with Frank. I have no doubt about his honesty.
When I asked him if I could post his entire report, with location details redacted, he courageously volunteered to attach his name to the sighting. In addition to the initial report, I’m including some further comments he made when I shared my impressions of the area and asked if I could include his description in the post. His words should speak for themselves.
I was a friend of Frank and talked to him on a few occasions about my own experiences with the IBWO. I saw a lone male when I was about 14 years old on my grandfathers property in West Central Louisiana. After many years of searching without success, I became a IBWO agnostic/ skeptic. I’m an avid hunter and the last two years I had pretty much given up on even thinking about the bird. Saturday morning that changed. I went on a annual squirrel hunting trip over the weekend . . . the birds presence there it never crossed my mind. On Saturday at approximately 9:30 am I was in pursuit of a squirrel . . . in a section of large trees. I saw through some brush a black animal with white stripes slowly making its way up the truck of a large tree. My first thought, was it was a black squirrel with white marks on it which would be the kill of a lifetime. I had killed a black squirrel the previous afternoon. My second thought, as the animal became more visible was that it was a skunk with white stripes somehow climbing up the bottom of the tree. Then suddenly, the bird came into better view and into the sunlight. I first noticed that it wasn’t climbing the tree slowly but was hoping or bobbing up the tree. I noticed the two clear stripes coming down from the neck to the lower back. When I reached for my phone in my front pocket the bird quickly turned its head in my direction. At that moment, I noticed the most startling thing I’ve ever seen. The bill on the bird was solid white. The sun illuminated its radiance as it stuck out against the dark bark of the tree. I noticed a black underdeveloped crest. Judging by the size and underdevelopment of the crest it was a fledgling. Suddenly, the bird flew to my right then ascended upwards and swung to my left where the bird was met in the air by a larger woodpecker without any red on its crest. The soaring birds quickly were no longer visible. I did not get the best view of them flying off because I was obstructed by trees and brush. I believe once again and have no doubt about what I saw. I know I won’t be taken seriously but do you think I should contact anyone . . . about this sighting?
Thank you for your steadfastness and detailed report. I wish I could have gone assisted you guys on the search. Unfortunately, a number of things required my attention. Mark you can use my name or report as you wish. I’m certain that I viewed at least one IBWO. I’ve typically hunted once or twice a week for about 17 years and I see Pileated Woodpeckers nearly every outing. I know the difference. A large Woodpecker with two white stripes, a long ivory bill, and a solid black crest stood out. Certainly, some will roll their eyes or be dismissive of my sighting. I’ve simply shared what I saw and the experience itself helped heal this doubting Thomas.
Steve Pagans and I visited the vicinity between November 16-21, spending a total of five days in the field and covering just over 23 miles. We had no possible sightings but heard what I’d describe as a weak possible single knock on the afternoon of the 21st. Because we were talking at the time, and there were some hunters in the vicinity, gunshot is a distinct possibility. I did not find the kinds of feeding sign I’ve suggested may be diagnostic for ivorybill; however, we did find several concentrations of bark scaling involving a variety of tree species. I usually post my trip reports as day-by-day logs, but since this involves a new area, I’ll take a different approach to summarizing our observations.
The area is part of a large parcel of bottomland hardwoods, much of it maturing second growth. Forest composition more closely resembles the old Project Coyote search area than the new one; Nuttall oaks, honey locusts, and pecans, which are absent from the new search area, are abundant. Overall, the forest is more mature than in the old search area, with many trees between 2′-3′ DBH, and some oaks and gums exceeding that in the most mature sections.
I have the impression that the harvest of cypresses from the area was limited. We only saw a couple of old stumps, and many seemingly healthy, large trees can be found, including the largest ones I’ve ever seen.
The woods are breathtakingly beautiful, and if ivorybills have persisted, I think the habitat is adequate to support them.
Woodpeckers and Nuthatches
Pileateds, Red-bellieds, Hairies, Downies, Flickers, and Yellow-bellied Sapsuckers were abundant, and impressionistically, there were many more Sapsuckers than in the current Project Coyote search area. By contrast, Red-headed Woodpeckers were scarce; we only heard three over five days. We encountered no White-breated Nuthatches (which are very common in our current search area) or Red-breasted Nuthatches and got no responses to playbacks of both species. Playback of the (putative ivorybill) March calls sometimes provoked apparent reactions from Red-bellied and Pileated Woodpeckers and from Red-shouldered Hawks.
Finding cavities can be challenging, especially when the canopy is high, leaves have not all fallen, and the mid-story is thick. In addition, Pileated Woodpecker cavities vary considerably, and there are no data on the dimensions of ivorybill roosts. All we know is that ivorybill nests tend to be larger and more irregularly shaped than Pileated nests. It seems reasonable to infer that the same would apply to roosts. While cavities may not be strong indicators of presence, it’s still worth looking for outliers. We found two on this trip, one in a honey locust (which has harder wood than most oak species) and one in an American elm.
As noted, we did not find any feeding sign that matches the diagnostic criteria I’ve hypothesized for ivorybill work. We did, however, find a decent quantity of bark scaling. Our field impression was that bark scaling was not as abundant as it is in our main search area, but on reviewing the photographs I took over five days, I’m doubting that impression.
We found bark scaling, some fresh some older, on a number of species – honey locust, sweet gum, red maple, persimmon (old and not photographed), and sassafras (not photographed and consistent with PIWO scaling on the species that I’ve found locally). The bark of small red maples is easy to scale, so this work too could well be Pileated.
In the area where we found the cavity in a honey locust, there appeared to have been a substantial die-off of that species, and several snags had scaling on the upper branches and boles. Honey locust bark is very hard and tight when the tree is alive and shortly after death, but it softens, loosens and becomes easy to remove, as was the case of the snag shown below. Examination revealed that the snag shown below was infested with termites, making PIWO the likely culprit, at least with regard to the most recent work.
There was scaling, both old and new, on a number of recently dead honey locusts in the vicinity.
The bark remained hard and very tight on the recently downed locust shown below; however, the appearance and extent of the scaling are suggestive of Pileated. Squirrel is also possible, although there were signs of insect infestation.
Sweet gum scaling was also abundant. Most of it was on higher branches and involved small limbs. The largest limb is shown in the first image below. Most of the chips were small, and all of the work strikes me as being within the range of what’s physically possible for Pileated. There was a time when some of this work would have excited me more. Nevertheless, the fact that bark scaling is abundant in the area is encouraging, since Pileated Woodpeckers scale bark relatively infrequently. In addition, scaling is likely to be less abundant at this time of year, when other food sources are readily available.
I always enjoy including herp photos when the opportunity presents itself. Steve nearly stepped on the rattlesnake, the biggest I’ve ever seen. I was glad to be wearing snake boots. The eastern ribbon and garter were mesmerizing.
Some Closing Thoughts
The forest is extensive. We focused on the vicinity of Joseph’s sighting, coming in from several different directions. Many acres remain to be explored. We found little beaver sign but understand that beavers are abundant in nearby, much less accessible patches of similarly mature forest. Hunters frequent the area, but as in many other patches of potential ivorybill habitat, signs of human activity – litter, shotgun shells, flagging – diminish the farther one goes from existing ATV trails.
While Steve and I didn’t see or hear anything strongly suggestive of ivorybill, I was very pleasantly surprised by the quality of the habitat. I came away convinced that this area merits further attention, and that would be the case even without Joseph’s report. There is far more such habitat in Louisiana than most casual followers of the ivorybill saga imagine, and while I plan to remain focused on the current Project Coyote search area, I will do my best to give this area the attention it deserves.
I returned to the search area last week and spent as much time as I could in the field. The trip was generally uneventful, and conditions – strong winds, rain, and high water – limited my field time. Woodpeckers are getting quieter generally; full leaf out, heat (temperatures in the high 80s on the 26th, 27th, and 28th), and abundant mosquitoes make things even more difficult at this time of year; nevertheless, I’m planning one more trip before summer.
On the 26th, I hiked to hickory stub that currently has two cameras trained on it, as one camera needed securing. There were no signs of woodpecker activity on the stub. This beautiful Great Egret in a beautiful spot was a highlight. There were Little Blue Herons in the vicinity too, but I couldn’t get a clear shot, too much mud and intervening vegetation.
On the 27th, I arrived at the “listening point” (where the March recordings were made) shortly after sunrise. I opted to sit quietly, rather than doing playback or ADKs. I did not see or hear anything.
I met up with Steve Pagans at around 10 am. Since water levels were low, we were able to get closer to the snag with the cavity that I found last month. I spotted a second cavity higher on the stub, on the opposite side.
These cavities are large, similar in size, shape, and unusual appearance. While I suspect they are no longer active roosts, we will put a camera on the snag in June, if it’s feasible to do so. The nest John Dennis found in Cuba appeared to have two entrance holes, although Dennis thought one might be too small.
On the hike out, I spotted this wolf spider with her young on her back.
On the 29th, Steve and I visited one of the less accessible parts of the search area. It is an impressive patch of forest, with some oaks and sweet gums approaching or surpassing 5′ DBH. The sweet gum below is probably the largest single trunked gum we’ve found.
Reminiscent of the Singer Tract.
Predicted wind speeds were 15-20 mph, and the gusts were undoubtedly stronger, so birds were not very active. The gusts were often unnerving, and a couple of large limbs fell, uncomfortably close to us, while we were stopped for lunch.
The forecast for the 30th was for even stronger winds, with thunderstorms in the afternoon. We decided to play it safe and stay out of the woods. Steve went home, and I spent part of the day driving scouting a large patch of nearby forest by car, but I wasn’t able to reach the bottomland area that had intrigued me on Google Earth.
The rains didn’t arrive until evening, but they were very heavy, with 3-4″ overnight. Thunderstorms continued until mid-morning on the 1st, so I didn’t venture out until about 10:30. Conditions were cool and cloudy, and everything was soaking wet. My movements were limited by high water levels; these continued to rise during the four hours I spent in the field. Avian activity was again minimal. Coming across this rattlesnake, the third or fourth I’ve found over the years, was the day’s highlight.
On May 2nd, my last field day, I spent the early morning trying to get to the hickory stub and trail cams. Water levels were too high, so I returned to my car and drove to a more accessible location. While I have been concentrating on it less this season, there have been a number of possible contacts in this area, and we have found abundant sweet gum scaling there every year. As has been discussed in several recent posts, classic, ‘Tanneresque’ high branch scaling on freshly dead sweet gums is not necessarily inconsistent with Pileated Woodpecker.
Still, I found some very dramatic work on the dead fork of a dying gum. Phil and I first found this tree in February, but most of the scaling has taken place since then. Of particular note were the enormous bark chips found at the base, again all removed since the end of January. My hat, which is shown for scale, is 12.5″ x 12″. Note that this scaling involves some of the largest limbs. Since some gum balls are still attached to the dead limbs, I think it’s safe to assume that the bark remains relatively tight; the scaling also looks generally clean, something that I find suggestive of ivorybill. To the best of my recollection, the bark chips are the largest I’ve ever found from sweet gum limbs.
Later that morning, I found a mildly intriguing cavity in a small sweet gum (~18″ DBH). While it’s almost surely PIWO, I’m including it because the shape and skewed angle are somewhat interesting and also to illustrate that even smaller trees can host substantial cavities. The original image was badly backlit, so I’ve brightened it and rendered it in black and white to make the cavity easier to see. Referencing Dennis again, he estimated the diameter of his Cuban nest tree at 12″. While DNA evidence suggests the Cuban IBWO is/was a different species, more closely related to the Imperial than to the US IBWO, the conditions under which Dennis found a breeding pair seem relevant to the survival of the North American species, and the ‘old growth specialist’ caricature:
There was a sprinkling of deciduous trees, some quite large. Although this region had been heavily logged and burned over as well, growth was quite luxuriant in spots. A watercourse, as well as the generally rugged terrain, had prevented a clean sweep of all the timber. The pine trees, on the whole, were limited to less than five inches in diameter.
There may be more on this in an upcoming post.
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.
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”.
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:
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.
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.
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%.
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 hardwoods, The 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.
Part 1 is here. Part 2 is here. I encourage you to read those posts first, as this one only adds a little to what’s been documented and discussed. Phil Vanbergen found an additional sequence this morning, one that shows the balance of the scaling that was done on the limb between December 22nd and January 26th.
In this sequence, Pileateds do most or all of the work that I had ascribed to squirrels. As in the other two sequences, the birds spent approximately fifteen minutes foraging, removing a couple of small patches from the lower part of the limb before working somewhat more extensively on the upper left. As in the other sequences, it appears that one bird did the vast majority of the work, but I haven’t found any frames that are well enough resolved to determine whether it was the female or the male. Per Phil, squirrels can be seen in additional sequences, “often poking around the scaled patches”.