The objectives of this research are to determine what factors limit or regulate populations of migratory birds that breed in the north temperate forests and winter in the Neotropics. The basic question concerns whether these factors operate more importantly in summer breeding areas at temperate latitudes, in neotropical winter quarters, or during both seasons. Through demographic and experimental studies, hypothesis will be tested to determine (1) if limitations occur in both summer and winter, (2) if habitat occupancy is determined by social dominance (despotism) or other preemptive behavior, (3) if individuals vary in fitness among habitats, that is, the demographic consequences of despotic habitat selection, and (4) what ecological variable affect habitat quality and therefore fitness. Emphasis will be on differential fitness among habitats in both summer and winter, including second-growth forests, agricultural lands, and other human-modified habitats. The results will advance our understanding of the population dynamics and community relations of these migrant bird species, as well as the factors affecting their population abundances. Such information also will contribute to the development of sound and effective conservation policies.
