Winter site fidelity of Prairie Warblers in the Dominican Republic

Wintering Prairie Warblers (Dendroica discolor) were studied in pine forest , desert them scrub, and desert wash habitats of the Sierra do Bahoruco, Do minican Republic from October-April 1996-1998 and January-February 1999. We used mist netting, color banding., and extensive resighting of color-bande d birds to quantify habitat-specific demographics, site fidelity, and fitne ss indices. Males predominated early in the season in pine habitat while fe males predominated in the desert. Sex ratios were more equal through the dr ier months of late winter although females continued to be more frequent in the desert. Adult birds predominated throughout all habitats and time peri ods. Nonterritorial wanderers were far more common in desert habitats than in pine forest, and females predominated among these wanderers. Site persis tence was moderately high, but variable between habitats and time periods, and was significantly lower in the drier months in thorn scrub than it was in the desert wash or pine forest. Annual return rates were generally high and did not vary significantly among years. Birds showed significant declin es in pectoral-muscle-mass scores in both of the desert habitats but not in the pine forest. Data presented here emphasize the importance of dry-seaso n events and habitat heterogeneity in the winter ecology of migratory birds .