Populations of permanent resident "Mangrove" and migratory "Yellow" forms of the insectivorous Yellow Warbler (Dendroica petechia) occur together in mangrove woodlands along the coasts of Middle America in winter. "Mangrove" Warblers are larger than "Yellow" Warblers, with proportionately longer bills, more rounded wings, and shorter legs. "Yellow" Warblers in the temperate zone use aerial foraging techniques more than "Mangrove" Warblers. In winter, "Yellow" Warblers shift their foraging behavior from their breeding pattern towards that of the "Mangrove" Warblers. / Based on intraspecific morphological differences, I made predictions about foraging differences between the two forms, and these predictions were tested by field observations of the two forms when they occurred together in mangrove habitat. As predicted, "Mangrove" Warblers were more adept at flying through the foliage and they foraged more slowly than did "Yellow" Warblers. However, "Mangrove" Warblers did not use aerial foraging actions more than the "Yellow" Warblers did, contrary to the predictions. / The predictions were also tested in a more controlled situation, in which wild-caught birds were used in aviary experiments. In this situation, "Mangrove" Warblers hovered longer and held their bodies more horizontally than did the "Yellow" Warblers. Because of the differences in body angle, "Mangrove" Warblers were able to hover closer to a vertical surface without their wing tips striking it, than could the "Yellow" Warblers. / The superior hovering ability of the "Mangrove" Warblers, detected only in the aviary experiments, confirmed predictions based on morphological comparisons, in spite of the fact that the differences were not evident from field observations even when the two forms occurred in one habitat. In fact, if only "Yellow" Warblers in the temperate zone and "Mangrove" Warblers had been compared, the predictions on foraging action would have been contradicted. To analyze ecomorphological problems it is necessary to minimize confounding factors. Even then, experiments may be necessary to fully understand ecomorphological relationships. / Source: Dissertation Abstracts International, Volume: 49-12, Section: B, page: 5126. / Major Professor: Frances C. James. / Thesis (Ph.D.)--The Florida State University, 1988.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77923 |
| Contributors | Wiedenfeld, David Alan., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 111 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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