Florida Scrub-Jay Demography in Different Landscapes

Abstract

AISTICT.--Florida Scrub-Jay (Aphelocoma coerulescens) demography and cooperative breed- ing were measured from 1988 to 1993 at two sites (HC and T4) on John F. Kennedy Space Center along Florida's Atlantic coast. The results from HC and T4 sites were compared with published results from the Archbold Biological Station in central Florida. The T4 population increased because of reproductive success and immigration, resulting in a nearly equal non- breeder 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 success, and the nonbreeder sex ratio was biased towards males. During the first nesting season after hatching, nearly one of every five HC females bred. Pairs with non- breeders (potential helpers) usually had greater reproductive success than pairs without nonbreeders at HC and Archbold, but not T4. Pairs with nonbreeders usually had greater survival than 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 contributed to differences in demographic patterns be- tween study areas. Received 3 fuly 1995, accepted 21 September 1995. MOST STUDIES on the Florida Scrub-Jay (Aphel- ocoma coerulescens) are from oak-dominated scrub at Archbold Biological Station (Archbold), where optimal habitat is excessively drained, contains many open sandy areas, and has few trees (Woolfenden and Fitzpatrick 1984, 1991). One of the largest contiguous populations of the fed- erally threatened Florida Scrub-Jay occurs on John F. Kennedy Space Center (KSC; Cox 1987). Most KSC habitat is composed of patches of scrub oaks in a matrix of poorly drained flat- woods vegetation and marshes (Breininger et al. 1991, 1995). Because of alterations of the nat- ural fire regime, most KSC habitat has taller vegetation and fewer openings than optimal Archbold scrub (Breininger 1981; Breininger and Schmalzer 1990; Schmalzer and Hinkle 1992a, b). Florida Scrub-Jays inhabit all-purpose terri- tories defended year-round by a permanently monogamous breeding pair (Woolfenden and Fitzpatrick 1984, Breininger et al. 1995). Except where subject to habitat loss and fragmentation, most Florida Scrub-Jays disperse short distances (one to three territory widths) and occupy a territory for life after becoming breeders. Young Florida Scrub-Jays usually remain as nonbreed- ers (potential helpers) with the breeders for at