Populations of migratory songbirds are limited by multiple environmental and ecological factors. Events occurring on the wintering grounds, the breeding grounds, and during migration all potentially affect their population size. Currently, the ecological mechanisms that control populations of migratory birds are poorly understood. Evidence based ecological correlations suggests that food abundance may be the most important winter-season factor limiting populations of migratory songbirds; however, no published experimental evidence exists to support this hypothesis for migrants in temperate or tropical wintering areas. Using the Ovenbird (Seiurus aurocapillus) wintering in Jamaica, we are investigating how experimental manipulations of food availability affect the behavior, physiology, survival, and migration departure timing of a migratory songbird. Based on estimates derived from these experimental and observational studies, we will construct a simulation model to investigate how populations may respond to climate change, which affects food abundance via patterns of changing rainfall. Model predictions will be tested by correlating long-term, continental-scale changes in Ovenbird populations, as measured by Breeding Bird Survey data, with historical records of climate and vegetation patterns from across the Ovenbird's winter distribution. We take a unique approach by using simulation modeling to link small-scale, field-based experimental tests of the mechanisms that limit migratory bird populations with well documented large-scale changes in population size of a widely distributed North American migratory bird species.
