This research will analyze the effect of landscape factors and interference competition on the abundance of a neotropical migrant, the Golden-winged Warbler (Vermivora chrysoptera). This species has declined and even disappeared from a large portion of its range. This decline has been attributed to a loss of breeding habitat, or to behavioral interactions with an invading congener, or to a loss of winter habitat. Field studies will determine the vegetative characteristics of the nesting habitat used by the Golden-winged Warbler alone and in sympatry with the Blue-winged Warbler (V. pinus). Landscape analyses, utilizing current and historical aerial photographs, will assess changes in the regional availability of nesting habitat, and will be correlated with changes in Golden-winged Warbler abundance. Habitat use with and without neighboring Blue-winged Warblers, and changes in use following experimental removal of Blue-winged Warblers will be determined. Nesting success will be related to Blue-winged Warbler proximity and to vegetative characteristics of nesting habitat. These studies will help determine if coexistence of these two congeners is limited more by specialized adaptations to a particular habitat or by their behavioral interactions. These analyses of the breeding season may provide insight about the relative significance of winter habitat loss. The results may also be of more general significance in light of rapid changes in global Climate and land use patterns.
