1999-287 - Laserfiche WebLink

Home Browse Search

i Z mortality, food habits, and habitat suitability were collected for a sample of 174 nests. Family size averaged 3.0 individuals per group with 630/0 of the breeding pairs accompanied by at least one helper. Clutch size averaged 3.8 and average brood size was 3.0 (Toland unpubl. data). Median incubation date was April 7'h and median hatching date was April 24"'. Approximately 72% of the nestlings successfully fledged. Mean annual productivity was 1.9 young fledged per pair per year. Median fledging date was May 10"' and 70% of all nesting attempts were successful in fledging at least one young (Toland unpubl. data). Habitat characteristics were assessed in one-half acre patches around each nest tree and categorized as optimal, suboptimal, ancillary, or lawn (Toland 1991). Nesting success (percentage of nest attempts that fledged at least one young) was positively correlated to nest site habitat quality; success rates for optimal, suboptimal, ancillary, and lawn were 91, 67, 48, and 25%, respectively. Habitat features comprising each scrub -jay territory were assessed and characterized as optimal contiguous, optimal fragmented, and suboptimal fragmented. Nesting success was positively correlated with territory quality; success rates for optimal contiguous, optimal fragmented, and suboptimal fragmented were 79, 77, and 59%, respectively (Toland 1991). Mean annual productivity of scrub -jays in the study area was 2.2 young fledged per pair in contiguous, optimal scrub; 1.8 young fledged per pair in fragmented, moderately developed scrub; 1.2 young per pair fledged in highly fragmented, suboptimal scrub; and about 0.5 young per pair in residential lawns. tong -term studies at Archbold Biological Station have previously documented that mean annual productivity of scrub jays is 2,0 young per pair per year in stable populations where natality counterbalances mortality (Fitzpatrick et a/. 1991). The subject demographic studies found that scrub jays dispersed at earlier ages and farther distances than is reported for contiguous natural scrub landscapes (Toland unpubl. data), A total of 64 dispersals were documented, including 40 females and 24 males (Toland unpubl. data). The mean dispersal distance by females was 2.4 miles (3.8 km) lrange=0.2 mi. (0.3 kin) to 5 mi. (8.0 kin)] and the mean dispersal distance by males was 0.9 miles (1.4 km) (range -0.6 mi. (0.075 kin) to 2.9 mi. (4.7 km)]. Four females were known to disperse 4 miles (6.5 km) between the most northern clusters of the north subpopulation and the Sebastian Highlands/Pelican Island Elementary School southernmost clusters (Toland unpubl. data). The longest dispersal was 5 miles from a female that emigrated into the Wabasso Scrub Conservation Area frorn a cluster located on the Sebastian Airport/Golf Course (Toland unpubl. data). Most of the documented dispersals in the City of Sebastian were 2 miles or less (80% of females and 92% of males) (Toland unpubl. data). Breininger (1999) docurnented similar patterns on the urbanized and extensively fragmented South Brevard County barrier island, where females dispersed an average of 4.5 miles (7.3 km) and reales dispersed an average of 0.6 miles (1.0 37