Meeting Abstract

P2.121  Saturday, Jan. 5  Flexural stiffness of woodpecker tails with respect to foraging ecology READER, L*; CARRIER, D; GOLLER, F; University of Utah; University of Utah; University of Utah L.Reader@utah.edu

The woodpeckers (Picidae: Picinae) exhibit a unique locomotor style: climbing vertically upwards on tree trunks while supported by a stiff tail. Members within the group, however, exhibit varying degrees of dependence on this strategy. Tail support is also critical to the birds’ ability to hammer into trees when excavating nests or foraging. Accordingly, we expected that the stiffness of tail feathers would correlate with foraging style – and that tails would be stiffest in species with: 1) a high degree of dependence on hammering, and/or 2) a high frequency of tail propping during vertical climbing. Some species forage on trunks infrequently, but are adept at hammering hard food items that make up their winter diets (i.e. Lewis’ woodpecker). Others drill less forcefully, but remain on trunks constantly to forage (i.e. sapsuckers).We examined whole-tail flexural stiffness of several genera along this spectrum. We found that tails of woodpeckers most dependent on trunk foraging and/or anvil-style hammering have higher flexural stiffness than those of ground foraging woodpeckers like flickers. Ground foragers – which still excavate nest cavities – have higher stiffness values than robins, which served as the outgroup. Additionally, flexural stiffness changes along the feather shaft; tails are more rigid near the base than the tip. This difference is most pronounced in trunk foragers/hammerers, indicating a greater need for a stiff lever arm and a flexible point of contact on the tree.