According to Tanner, Ivory-billed Woodpeckers, “When feeding by knocking off bark . . . hit sidewise blows from both directions, and often pry and knock off the pieces of bark with a flick of the bill”. He wrote that the bark chips produced in this manner range from the “size of a silver dollar to the size of a man’s hand” when the bark is tight; looser bark “is detached in even larger pieces.” According to a photo caption in Arthur Allen’s 1937 National Geographic account of the Allen and Kellogg expedition, “To locate a nest, Dr. Allen searched for the large chunks of bark which the bird strips from trees.”
There are a couple of clear images of bark chips left behind by Ivory-billed Woodpeckers, and both of them are considerably larger than what Tanner described. These appear to be from trees where the bark had loosened or fractured.
Plate 10 in Tanner, Nuttall oak bark chip with beetle larvae.
We have found many similar chips beneath scaled trees, in both of our search areas. As discussed in this post, chips left by Pileated Woodpeckers (which are anatomically less well-suited to removing bark) tend to be smaller, thinner, and less dense, and Pileateds often scale in layers rather than removing bark all the way down to the sapwood with a single strike. Many of the chips we’ve found appear to have bill marks that are consistent with a powerful blow from a chisel shaped bill. As Frank puts it, think of the difference between a chisel (ivorybill) and an icepick (pileated).
The bark chips shown here are from dying trees, recently dead, tight-barked snags, or dead parts of live trees – sweet gums, hickories, oaks, honey locusts, and hackberries. Most were in a very early decay stage, probably earlier than Tanner’s plate 10. Many of these images appear in various posts on this blog, but I thought there might be some value in aggregating them, without further commentary.
A commenter on Facebook suggested that the apparent strike marks might be exit tunnels from wood boring insects and asked how it can be verified that the chips had not been shed due to stochastic events. I think its worth addressing these questions, since images often fail to convey context. Regarding the insect tunnel suggestion: there are no large exit tunnels visible elsewhere on the chip. As for the idea that these chips fell due to some natural process, most of the chips came from work on boles of trees or on blowdown; thus it was possible to assess bark adherence. In many instances, strike marks were visible on the trunks as well. There can be no question that this is woodpecker work. This includes some chips that are as much as 12 inches long and 6 inches across.
The exceptions are the extremely large chips – 2 from an oak (with my boot shown for scale), another from a different oak (also with a boot for scale), a couple from hackberries and one from a honey locust (on the windshield.) Most of these came from large branches that were too high to directly examine. The single large oak chip came from higher on the bole of a tree that had been extensively scaled in a manner that we think is consistent with ivorybill work and similar to what’s shown on the homepage, but it too could not be directly examined. Thus, I cannot be absolutely certain these did not fall naturally, but these were large, dense, heavy chunks of bark. Taking this and a number of other factors, including my field impression, into account, I do not think they fell on their own. Even if they did, they represent a small, outlying minority of the chips we’ve found over the years.