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Updated with More Pileated Woodpecker Clips: Trail Cam Results and More on a Camera Trap Tree

The original post from last week is below the updated material. It provides some important background, and I encourage you to read all the way and watch the clips.

A couple of prefatory notes for new readers: first, this discussion pertains to hickories only because the bark of trees in the genus Carya has characteristics that make it much harder to remove than any other type of tree in the southeastern U.S. Second, the video clips are time-lapse composites of images shot at 20 second intervals.

I’ve gone through most of the June-August captures from the deployment discussed in the original post and have found a number of additional examples showing one or two Pileated Woodpeckers foraging on the scaled areas. I’m including those captures and a couple of individual frames that should help illustrate what’s being described.

Pileated visits to the target tree spiked starting on June 17, with two visits on that day, one on June 18, and one on the 20th, 23rd, 24th, 25th, one on July 2, and two on July 3. There were no hits between July 4 and July 10 and no hits between August 2 and August 12. Imagery for July 11-August 1 has yet to be reviewed.

Of the sequences below, the ones from June 17, 18, and 25 are probably the most informative. They suggest that when Pileateds remove hickory bark, even on a tree that is considerably more decayed than some on which we’ve found scaling, they do so by focusing on the scaled edges, and when they do remove bark, they’re more likely to dig through it (as I’ve hypothesized) than to pry it off in flakes.

We have now obtained 22 sequences of Pileated Woodpeckers investigating or foraging on and around extensively scaled hickory boles, the first one dating back to 2013. Some captures involve lone birds and others involve pairs. Duration of the visits ranges from under 1 minute to upwards of 20 minutes. In these captures, Pileated Woodpeckers remove bark in modest quantities and with difficulty, when they remove it at all. They never scale extensively or remove bark in pieces approaching the size of those found under the homepage tree, and there is nothing in the footage obtained that suggests they are capable of doing so. I think this tends to exclude Pileated Woodpecker as the source of the initial work on hickories.

Hickory2Chips

Suspected IBWO hickory chips

 

 

 

 

These stills should shed additional light on Pileated Woodpeckers and bark removal.

 

The additional sequences are below, followed by the text of the original post.

 

 

 

 

 

 

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I just returned from Louisiana where I visited both the search area and the location of Joseph Saucier’s sighting last year. There were no possible encounters on this trip and just a little of potential significance ivorybill-wise. I plan to post a trip report within in the next week or so and hope to get to the long-promised evidence post in November. There may be additional posts about trail cam results if anything significant shows up. There are numerous cards to review, and I have a lot going on in a variety of arenas, but I’ll do my best to keep you all updated on a regular basis.

I’ve gone through the card for one of our deployments between August 21-October 20. The June to August card has yet to be reviewed, but these results are informative in their own right, especially in conjunction with the results from April and May, discussed here. I think they tend to support the hypothesis that Pileated Woodpeckers are not responsible for the bulk of the bark removal on live or recently dead hickories and at least indirectly to support the hypothesis that Ivory-billed Woodpeckers are the only creature capable of doing this type of work. (Go here for a discussion of squirrels as a potential source.)

At Tommy Michot’s suggestion, we’re also going to start quantifying our results, including all hits that we note, regardless of what kind of animal is involved. Those results appear at the end of the post.

Like two other current target trees, which are sweet gums not hickories, I selected this one because it had already been scaled (extensively in this case); the remaining (majority of) targets have been chosen in hopes that they will be scaled in the future. For most of the hickories we’ve found, including ones that I’ve watched for extended periods of time, the bulk of the scaling appears to have been done in a single visit.

We’ve found only one example of a tree with truly fresh scaling, the home page tree. That work, found in May 2013, was probably no more than a week old, since the trunk was wet with sap and the tree died soon after. Numerous large chips were found at the base. All other examples appear to have been less recent, and in most instances, flooding appeared to have washed bark chips away.

After reviewing the captures, I was inspired to revisit the history of this particular snag, which Phil Vanbergen found in early March, 2017. It had been extensively scaled at that time, I suspect during the spring or summer of 2016 but possibly the year before. Phil found a few small chips at the base, but given the extent of the scaling, it is safe to assume that the overwhelming majority of the chips associated with the initial work had been washed away in one of the flooding events that had taken place during the intervening months. Phil shot this video of the tree, which shows the work extending from mid-bole up to the point where the crown had broken off; I later found what I believe to have been the crown, and it too had been scaled.

 

 

 

 

 

 

 

Bark Strips

Small Strips Found by Phil Vanbergen at Base of Scaled Hickory, Presumed Source is Pileated Woodpecker

IMGP4590

Downed Hickory Top showing suspected ivorybill scaling.

What sets this tree apart, is that there appears to have been a second extensive scaling event between March 2017 and March 2018 when I re-found it. While there had been a couple of floods in the course of the year, one large and a couple of medium-sized chips remained near the base of the snag, but it was apparent that most had been washed away.

 

 

 

 

 

 

We deployed a trail cam on the tree in April, and one of the early frames from that deployment more clearly shows the extent of the second round of scaling, which reaches to near the base of the snag.

A comparison of that frame, one from the beginning of the mostly unreviewed June-August card, and a capture from October 21 of this year shows how little bark has been removed by Pileated and other woodpeckers over the course of just under six months, with modest quantities removed from the bole, as indicated by the arrows.

 

 

 

 

 

 

 

Pileated Woodpeckers appeared in two captures between late August and late October, a far lower rate than in April and May. The first capture, from September 24, involved one bird, which spent several minutes on the target tree and did little additional damage. The other, from October 5 involved two birds and was fleeting but cool to see. The time lapse clip and the three captures are below

 

 

 

 

 

 

 

 

 

 

 

 

Pileated Woodpeckers are abundant in the area, but we have yet to obtain any evidence that they can remove large chunks of bark from the boles of live or recently dead hickories and scale them rapidly and extensively; indeed, all the evidence obtained thus far is that they remove bark in small pieces, slowly and inefficiently.

Past observations suggest that the peak period for scaling of these hickories is between May and October. This appears to be the time frame when Hesperandra polita, the heartwood dwelling Cermabycid identified as infesting one of our scaled hickories, are likeliest to be  found under the bark, as larvae and adults, or close to the bark layer in pupation chambers. The adults shown below were collected from under bark on June 28, 2013.

 

 

 

 

 

In the case of this snag, at least, Pileated Woodpeckers removed little bark during the probable peak scaling period. The other side of the tree remains unscaled. In addition, we’ve found this work infrequently over the years, and the scaling on the lower part of this tree is the only new example of this kind of foraging sign found in the past year. All of this points to something other than Pileated Woodpecker, and I would suggest something rare, as the source of the scaling.

Regarding the hits over the course of the deployment, I’m counting a “hit” as the appearance of an animal in a frame or series of frames, including interrupted series in which the animal reappears after a break of a minute or two. Impressionistically, this deployment is considerably more active than some. Even so, there were no hits on 17 of 62 days.

The most frequent hits were lizards (mostly on the target tree): 46 hits.

Passerines, including Hooded Warblers, Carolina Wrens, and Cardinals, were next with 24 hits, followed closely by squirrels with 22.

Woodpeckers followed – 2 Pileated hits, one involving two birds, one Downy and one probable Yellow-bellied Sapsucker toward the end of the deployment.

There were two hits each for beaver, deer, and moth or butterfly (one likely a luna moth).

Finally, there was one apparent Barred Owl and only one hog, which was surprising given their abundance in the area.

Stay tuned for the trip report . . .

 

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Trail Cam Results and More on a Camera Trap Tree

I just returned from Louisiana where I visited both the search area and the location of Joseph Saucier’s sighting last year. There were no possible encounters on this trip and just a little of potential significance ivorybill-wise. I plan to post a trip report within in the next week or so and hope to get to the long-promised evidence post in November. There may be additional posts about trail cam results if anything significant shows up. There are numerous cards to review, and I have a lot going on in a variety of arenas, but I’ll do my best to keep you all updated on a regular basis.

I’ve gone through the card for one of our deployments between August 21-October 20. The June to August card has yet to be reviewed, but these results are informative in their own right, especially in conjunction with the results from April and May, discussed here. I think they tend to support the hypothesis that Pileated Woodpeckers are not responsible for the bulk of the bark removal on live or recently dead hickories and at least indirectly to support the hypothesis that Ivory-billed Woodpeckers are the only creature capable of doing this type of work. (Go here for a discussion of squirrels as a potential source.)

At Tommy Michot’s suggestion, we’re also going to start quantifying our results, including all hits that we note, regardless of what kind of animal is involved. Those results appear at the end of the post.

Like two other current target trees, which are sweet gums not hickories, I selected this one because it had already been scaled (extensively in this case); the remaining (majority of) targets have been chosen in hopes that they will be scaled in the future. For most of the hickories we’ve found, including ones that I’ve watched for extended periods of time, the bulk of the scaling appears to have been done in a single visit.

We’ve found only one example of a tree with truly fresh scaling, the home page tree. That work, found in May 2013, was probably no more than a week old, since the trunk was wet with sap and the tree died soon after. Numerous large chips were found at the base. All other examples appear to have been less recent, and in most instances, flooding appeared to have washed bark chips away.

After reviewing the captures, I was inspired to revisit the history of this particular snag, which Phil Vanbergen found in early March, 2017. It had been extensively scaled at that time, I suspect during the spring or summer of 2016 but possibly the year before. Phil found a few small chips at the base, but given the extent of the scaling, it is safe to assume that the overwhelming majority of the chips associated with the initial work had been washed away in one of the flooding events that had taken place during the intervening months. Phil shot this video of the tree, which shows the work extending from mid-bole up to the point where the crown had broken off; I later found what I believe to have been the crown, and it too had been scaled.

 

 

 

 

 

 

Bark Strips

Small Strips Found by Phil Vanbergen at Base of Scaled Hickory, Presumed Source is Pileated Woodpecker

IMGP4590

Downed Hickory Top showing suspected ivorybill scaling.

What sets this tree apart, is that there appears to have been a second extensive scaling event between March 2017 and March 2018 when I re-found it. While there had been a couple of floods in the course of the year, one large and a couple of medium-sized chips remained near the base of the snag, but it was apparent that most had been washed away.

 

 

 

 

 

We deployed a trail cam on the tree in April, and one of the early frames from that deployment more clearly shows the extent of the second round of scaling, which reaches to near the base of the snag.

A comparison of that frame, one from the beginning of the mostly unreviewed June-August card, and a capture from October 21 of this year shows how little bark has been removed by Pileated and other woodpeckers over the course of just under six months, with modest quantities removed from the bole, as indicated by the arrows.

 

 

 

 

 

 

Pileated Woodpeckers appeared in two captures between late August and late October, a far lower rate than in April and May. The first capture, from September 24, involved one bird, which spent several minutes on the target tree and did little additional damage. The other, from October 5 involved two birds and was fleeting but cool to see. The time lapse clip and the three captures are below

 

 

 

 

 

 

 

 

 

 

Pileated Woodpeckers are abundant in the area, but we have yet to obtain any evidence that they can remove large chunks of bark from the boles of live or recently dead hickories and scale them rapidly and extensively; indeed, all the evidence obtained thus far is that they remove bark in small pieces, slowly and inefficiently.

Past observations suggest that the peak period for scaling of these hickories is between May and October. This appears to be the time frame when Hesperandra polita, the heartwood dwelling Cermabycid identified as infesting one of our scaled hickories, are likeliest to be  found under the bark, as larvae and adults, or close to the bark layer in pupation chambers. The adults shown below were collected from under bark on June 28, 2013.

 

 

 

 

In the case of this snag, at least, Pileated Woodpeckers removed little bark during the probable peak scaling period. The other side of the tree remains unscaled. In addition, we’ve found this work infrequently over the years, and the scaling on the lower part of this tree is the only new example of this kind of foraging sign found in the past year. All of this points to something other than Pileated Woodpecker, and I would suggest something rare, as the source of the scaling.

Regarding the hits over the course of the deployment, I’m counting a “hit” as the appearance of an animal in a frame or series of frames, including interrupted series in which the animal reappears after a break of a minute or two. Impressionistically, this deployment is considerably more active than some. Even so, there were no hits on 17 of 62 days.

The most frequent hits were lizards (mostly on the target tree): 46 hits.

Passerines, including Hooded Warblers, Carolina Wrens, and Cardinals, were next with 24 hits, followed closely by squirrels with 22.

Woodpeckers followed – 2 Pileated hits, one involving two birds, one Downy and one probable Yellow-bellied Sapsucker toward the end of the deployment.

There were two hits each for beaver, deer, and moth or butterfly (one likely a luna moth).

Finally, there was one apparent Barred Owl and only one hog, which was surprising given their abundance in the area.

Stay tuned for the trip report . . .

 


Recent Trail Camera Results Part 2: Squirrel(s) on a Sweet Gum Stub

Summary

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.

Background

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.

P1170436

Upper Part of Scaled Surface Showing New Work

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.


Another Pileated Scaling Sequence – January 11, 2017

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”.

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