The influence of natural selection on wood-warbler morphology

Widem, Ann
Tom Wessels, MA
Department of Environmental Studies
Wing length, as an indicator of morphological variation, was examined in 33 species of Northeastern wood-warbles (Parulinae). I attempted to correlate wing length with migration distance in order to demonstrate the influences of natural selection on morphology. Data were taken from 28 years of banding information for migratory warblers passing through Manomet Observatory on Cape Cod Bay in Massachusetts. Fall 1996 data were collected by me, other Field Biology Training Program students, research assistants, and volunteers. The results of my study failed to find a correlation between mean wing length and migration distance. However, I did demonstrate a reduction in wing length variability from pre-migration birds to post-migration birds. This result agrees with other findings in the literature which report a significant influence of natural selection on morphology, as a consequence of bird migration. These findings demonstrate the need for further study of ecomorphology in migratory avian species. As the populations of many migratory birds continues to decline, the connections between evolutionary adaptations, species' ecology, and habitat destruction are crucial to preservation of many avian species as well as the entire ecosystem within which the reside.

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