|Foraging marks on
freshly dead trees
In Louisiana, Ivory-billed Woodpeckers were reported to forage by prying off sections of tightly adhering bark from the trunks of trees that had recently died. Many species of woodpecker will feed by probing under bark, but the bills of Ivory-billed Woodpeckers are large and flattened at the tip allowing them to strike thick strong bark cleanly away from the sapwood.
Throughout our study area along the Choctawhatchee River we observed sections on the trunks of freshly dead trees where tightly adhering bark had been scaled from large trees. This bark scaling was unlike woodpecker foraging sign that we observed in other southern forests. In many instances, such bark scaling revealed large bore holes of beetles. Spruce pine and sweet gum seemed to be the tree species that were most often scaled in this manner. In attempt to quantify the uniqueness of the bark scaling that we observed along the Choctawhatchee River compared to what we observed in other southern forests we compared the adhesion of the bark on woodpecker foraging trees in our ivorybill study site and to the adhesion of bark on woodpecker foraging trees in three creek bottoms around Auburn, Alabama where ivorybills almost certainly do not occur. For this comparison, we did not just choose the “best” trees on our Florida site. Within a patch of forest we measured bark adhesion on all trees greater than 4 centimeters DBH that had signs for woodpecker foraging. The bark adhesion on scaled trees along the Choctawhatchee River was significantly stronger than bark adhesion on trees around Auburn. The mean size of foraging trees in these samples was not different.
A priority of future research will be to provide better links between the scaled bark that we observe on trees along the Choctawhatchee River and foraging ivorybills. If we can demonstrate that such foraging sign is diagnostic of resident ivorybills, then a search for scaled bark can be used as a fast and efficient means to search forested areas for the presence of ivorybills.
|All information on this
copyright Geoffrey Hill and Daniel Mennill.
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