The specific causes of population declines of migratory birds are poorly understood. A major hypothesis to explain the declines is human-caused habitat conversion and loss in the tropical wintering grounds of the migratory birds. The objective of this research is to assess the ecological health of migrant land birds in human-modified versus natural habitats in Jamaica, West Indies. This island includes mangroves and Caribbean tropical dry forest, and human-modified habitats of citrus and coffee orchards, grazed second-growth scrub, and the ecologically complex rural residential areas. Within each habitat the investigators will quantify (1) abundance of resident and migratory birds, (2) overwinter survival of selected migratory species, (3) indicators of bird condition for the selected species, and (4) seasonal patterns of food resource availability capable of supporting the observed bird populations. These data coupled with experimental manipulations of resource abundance will allow the investigators to test alternative hypotheses explaining the ecological bases for the individual and population responses to these different habitats. The results of this research will be immediately applicable to conservation of animal populations by indicating which human activities are most compatible with maintenance of biotic resources in tropical Caribbean countries. The effects of habitat-specific land-use on avian consumers and their food resources is critically needed for the development of ecologically sound and effective wildlife-conservation recommendations.
