| In this dissertation, I examined the Bahama Oriole (Icterus northropi ) at multiple scales, with the aim of developing a sound management plan for this critically endangered bird. In the first of five studies, I measured plumage variation among four allopatric populations of the former Icterus dominicensis complex in the Caribbean. Diagnosable plumage differences among populations contributed to the subsequent elevation of each of these populations (including northropi) to species status. In the second study, I examined molecular variation in subpopulations of I. northropi on North Andros, Mangrove Cay, and South Andros, The Bahamas. I identified several patterns of genetic variation that will inform conservation planning. The third study explored the population status and breeding ecology of the Bahama Oriole. My estimates of 141--254 individuals remaining globally contributed to an IUCN Red List designation as "critically endangered." Orioles selected nesting trees that were significantly taller, less likely to have shrubs underneath, farther from cover, and with more palm trees nearby than randomly available palm trees. Lethal yellowing disease devastated coconut palms regionally on North Andros during the course of our study, but palms on South Andros and Mangrove Cay, where oriole density was higher, remained healthy. In the fourth study, I assessed the Bahama Oriole's community-level relationships, including the relative densities of other avian species in three habitats (pine forest, coppice, and anthropogenic habitat), foraging strategies, and inter- and intraspecific social interactions. My findings indicate coppice is vitally important to resident, migrating, and wintering birds. Collectively, these studies identify key conservation priorities to save this critically endangered bird. In my final study, a literature review, I explored the ecological consequences of extinction in a well-studied insular model: the Hawaiian Islands avifauna. Five of six islands have significantly different trophic guild structure now than they did prior to the arrival of humans, due to a combination of extinction events and introduced bird species. Very few extinct bird species have been replaced by equivalent ecological substitutes in the present day avifauna, leading to coextinctions of dependent species. This research highlights the importance of preventing extinctions in the remaining global avifauna. |
