Mon, Aug 02, 2021:On Demand
Background/Question/Methods
New World wood warblers (Parulidae) represent one of the most dramatic adaptive
radiations in North America. However, the ecological bases for the morphological
differences among these species remain poorly understood, especially considering how
many foraging and habitat studies the family has inspired. MacArthur’s (1958) classic
ecological study demonstrated that foraging differences allow for coexistence of
breeding spruce-woods warblers, but he downplayed the importance of morphology
in shaping these relationships. We hypothesized the existence of relationships between
morphology and diet in a suite of parulid warblers. We combined a principal component
analysis (PCA) of 18 external morphological traits of 11 species of warblers with stomach-
content data from coexisting species in one breeding community in Louisiana and three
wintering communities in Jamaica.
Results/Conclusions The primary morphological differences, corresponding with the first three PCA axes, were body size, morphological adaptations for aerial foraging versus gleaning, and arboreal versus ground-foraging adaptations. Our analysis revealed little morphological overlap among the 11 species. Differences in diet among the warblers showed a significant relationship to the first two PCA axes of morphological traits. For five coexisting, foliage- gleaning species wintering in Jamaican wet limestone forest, larger warblers ate larger beetles and Orthopterans but not larger ants. In analyses including all four communities, species of warblers with aerial foraging morphologies consumed a greater proportion of winged insects than other warbler species. These findings document prey selection relevant to multiple subtle morphological differences among coexisting species. Overall, our results indicate that food and foraging have likely played an integral role in the morphological diversification and coexistence of species in the family Parulidae.
Results/Conclusions The primary morphological differences, corresponding with the first three PCA axes, were body size, morphological adaptations for aerial foraging versus gleaning, and arboreal versus ground-foraging adaptations. Our analysis revealed little morphological overlap among the 11 species. Differences in diet among the warblers showed a significant relationship to the first two PCA axes of morphological traits. For five coexisting, foliage- gleaning species wintering in Jamaican wet limestone forest, larger warblers ate larger beetles and Orthopterans but not larger ants. In analyses including all four communities, species of warblers with aerial foraging morphologies consumed a greater proportion of winged insects than other warbler species. These findings document prey selection relevant to multiple subtle morphological differences among coexisting species. Overall, our results indicate that food and foraging have likely played an integral role in the morphological diversification and coexistence of species in the family Parulidae.