Sexual differences in foraging behavior in two species of Dendrocopos woodpeckers

Publication Type:

Journal Article

Authors:

Ligon, J. D.

Source:

Auk, American Ornithologists' Union, Volume 85, Issue 2, p.203-215 (1968)

Call Number:

A68LIG01IDUS

URL:

https://sora.unm.edu/node/21713

Keywords:

Arizona Woodpecker, Dendrocopos arizonae, Dendrocopos borealis, Red-cockaded Woodpecker

Abstract:

The Red-cockaded (Dendrocopos borealis) and Arizona (D. arizonae) woodpeckers demonstrate sexual differences in foraging behavior. In the former species there is little morphological correlation with the behavioral differences, whereas in the latter a pronounced sexual difference in bill length exists. Males of D. borealis forage to a large degree on the branches and twigs of pines, while the females forage almost exclusively on the trunk, often at low elevations. The two sexes of D. arizonae also forage in different parts of the trees but overlap much more than in D. borealis. In D. arizonae the differences in beak size can be correlated with differences in foraging techniques, thus the sexes may utilize the same portions of the trees in somewhat different ways. Two possible mechanisms for the evolution of sexual foraging differences are discussed. The first assumes a limited food supply, with selection favoring those individuals that are most efficient in utilizing the food resources of their habitat. Dominance of one sex (male) is suggested as an important factor in stabilizing sexual differences in feeding behavior. Secondly, differences in foraging could have arisen primarily by selection for those birds that cooperate best with their mates. A secondary result of selection for increased compatibility is a more efficient utilization of the habitat. Possible reasons that some trunk foragers appear to demonstrate sexual differences more conspicuously than do birds that do not forage on trunks include: (1) the long-term nature of the pair bond in some species requiring compatibility between members of the pair; and (2) a reduced accessibility or quantity of foods on tree trunks as compared with other foraging sites.