A comparison of foliage discrimination learning in a specialist and a generalist species of migrant wood warbler (Aves: Parulidae)

Abstract

The Bay-breasted Warbler (Dendroica castanea) is more generalized in its foraging behavior than the Chestnut-sided Warbler (Dendroica pensylvanica) where the two species winter together in Panama. I tested the hypothesis that the Bay-breasted Warbler would learned to discriminate between foliage types of differing profitability more rapidly than the more specialized Chestnut-sided Warbler. The performance of the two species in a laboratory discrimination experiment involving two foliage types was similar. Both species learned the foliage discrimination rapidly, in an average of 22 trials. Extinction occurred at a similarly rapid rate (17 trials) in both species as well. Differences in apparent foraging plasticity between the two species may be based primarily on their different responses to novelty, rather than differences in learning abilities. None of the warblers showed any tendency to attempt to solve the problem based on the irrelevant spatial cues prior to acquiring the correct response. Visual discrimination problems based on habitat cues are more relevant to insectivorous birds than are the more commonly administered spatial learning problems.