Bark Scaling Gallery 2009-2015
I’ve collected examples of bark scaling that we think is suggestive of or diagnostic for Ivory-billed Woodpecker from various pages on the site that include a good deal of analysis (although I’ve included a more analytical addendum at the bottom of this page.) I think the images speak for themselves, and many aspects of the gestalt we rely on in the field should be apparent. Most of the work (other than that described as old) was on recently dead trees or dead parts of living ones, although the hickory (also shown on the homepage) was wet with sap when we found it and apparently died soon after. The bark on that tree was so tight that it could only be removed with a hatchet. When examination was possible, bark was tight and could either only be removed with an implement or was very difficult to remove by hand; twigs and sometimes leaves still attached. The downed trees shown had all fallen and died recently, probably within no more than six months; twigs were still attached on all of them and leaves on most. Also in most cases where examination was possible, very large bark chips were found at the base of the tree, some as long as my forearm, several inches across, with many a quarter inch thick.
In Tanner’s description of ivorybill feeding preferences, the kind of wood they “habitually feed upon” had been dead for “only for a year or two”, while Pileateds prefer longer dead snags. (p. 51). While I think Tanner overemphasized freshly dead trees as a food source (as Plates 9-11 suggest), I’m confident that the vast majority, if not all, of the work shown here falls well within those parameters, or indeed involves trees that died considerably more recently, as the presence of leaves suggests.
Tanner was fairly cryptic about identifying criteria for bark scaling, but he relied on it as the strongest indicator of ivorybill presence. From his notes: “This leaves patches of exposed wood, usually with a reddish tinge because of the frass, on limbs and trunk where the bark is otherwise hard and tight.” He also wrote that IBWO scaling is more extensive than Pileated, calling Pileated scaling “spotty” by comparison. In the monograph, he wrote that Pileated scaling is mostly “on loose bark and was never as cleanly done or extensive as the work of the Ivory-bills” and the ivorybill ” . . . is capable of easily scaling away heavy bark that other woodpeckers could not loosen. Even the Pileated is not able to remove hard, tight bark with anything like the speed of the Ivory-bill.” His observations suggested that scaling comprised 23% of Pileated foraging behavior. A more recent and probably more relevant study from central Louisiana showed Pileateds scaling a mere 7% of the time (Newell, 2010).
Over the past eight years, I have visited many locations where ivorybills have been reported and have studied bark scaling in areas outside the historic range. I have found an abundance of the types of work shown below only in two Louisiana locations. In our current search area, we’ve often found this scaling in concentrated pockets.
For a more in depth discussion of many of these images, our hypothesis about bark scaling, the field observations, and scientific literature that informs it, visit the posts tagged “cavities and feeding sign”, this one and this one in particular.
Updates to this page will be posted above the original images included in the gallery, most recent first. The original gallery is in chronological order, November 2009 – February 2015.
Update: March 2015:
We found an abundance of recent feeding sign on sweet gums, both standing and downed, as well as some older work we think of as diagnostic on dead hickories. This is discussed in detail in Part 1 of the trip report. Many of those images (some with exposure adjusted) are included here. Several others were not included in that post.
End of update.
An additional insight followed the initial creation of this page, and this seems like the appropriate place to include it. There appear to be two types of work in these images, both consistent in many respects with what is known about ivorybill feeding.
One is scaling on what appear to be cerambycid-infested trees. Cerambycids are known to be a preferred ivorybill prey species, and we found adults of a known prey species (Hesperandra or Parandra polita) under the bark of one of the scaled hickories. This type of scaling reveals numerous, large exit tunnels and virtually no frass. This work is found on boles and large branches, and I suspect that it may have to be done very rapidly and efficiently because the window of time for capturing larvae as they dig their exit tunnels before creating a sealed chamber and pupating is likely quite narrow. This seems suggestive of IBWO, since efficient scaling and a high degree of specialization in terms of targeting this particular prey at the right time, when the larvae are at their most nutritious, are consistent with both morphology and known behavior; for a Pileated, the time and effort involved would likely exceed the reward. The long temporal gap between or lack of return visits to these feeding trees might also point in this direction.
This type of scaling seems to involve the first infestation with and maturation of cerambycid larvae. The last time I visited the hickory that appears on the home page, approximately 18 months after finding it, there was no new scaling (the bark was of course quite loose) and a little bit of apparent Red-bellied excavation. There did not appear to be any new exit tunnels either. The same is true for the sweet gum shown just below it.
The second category involves trees that are predominantly infested with larvae that live just under the bark. These generally have shallow galleries and few or no exit tunnels; frass is often visible when the work is fresh. We’ve found this work on boles of smaller trees and on the boles and tops of downed, but very recently dead sweet gums – twigs attached (in all) and leaves attached (in most) instances. The reddish tinge from the frass that Tanner described is visible in some of the images above. I suspect this type of scaling is less dependent on season.