The objectives of this research are to determine what factors limit or regulate populations of migratory birds that breed in north temperate forests and winter in the Neotropics. the basic questions 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, hypotheses will be tested to determine (1) if limitation occurs in both summer and winter, (2) if habit occupancy is determined by social dominance (depotism) 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 variables affect habitat quality and therefore fitness. Emphasis will be on differential fitness among habitats i 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 will also contribute to the development of sound and effective conservation policies.
