FLORIDA SCRUB-JAY DEMOGRAPHY IN DIFFERENT LANDSCAPES

Florida Scrub-Jay (Aphelocoma coerulescens) demography and cooperative breeding were measured from 1988 to 1993 at two sites (HC and T4) on John F. Kennedy Space Center along Florida's Atlantic coast. The resul ts from HC and T4 sites were compared with published results from the Archbold Biological Station in central Florida. The T4 population incr eased because of reproductive success and immigration, resulting in a nearly equal nonbreeder sex ratio. Nearly all young Florida Scrub-Jays delayed breeding for at least two years after hatching at T4, similar to Archbold. The HC population decreased because of poor nesting succ ess, and the nonbreeder sex ratio was biased towards males. During the first nesting season after hatching, nearly one of every five HC fema les bred. Pairs with nonbreeders (potential helpers) usually had great er reproductive success than pairs without nonbreeders at HC and Archb old, but not T4. Pairs with nonbreeders usually had greater survival t han pairs without nonbreeders at Archbold, but not at HC or T4. Female breeder mortality was slightly higher than male breeder mortality at T4 and HC, but not at Archbold. Evidence suggested that predation cont ributed to differences in demographic patterns between study areas.