Breeding biology and productivity of Florida's Crested Caracaras

I studied the breeding biology of Crested Caracaras (Caracara plancus) in s outh-central Florida from 1994 through 1996. Reproductive activity was moni tored year-round on 30, 48, and 55 territories, respectively. Pairs remaine d on breeding territories throughout the year and exhibited strong fidelity to the nest site between years; however, annual turnover rate among known breeding individuals was approximately 18%. Territorial occupancy and breed ing rates on known occupied territories averaged 95% and 98%, respectively. Observed patterns of breeding activity and nesting success suggested a lin k between reproduction and precipitation. Active nests were found from Sept ember through June, but most nesting activity corresponded with the dry sea son, November through April. Egg laying in many pairs occurred following an abrupt decline in precipitation in the fall each year. The overall probabi lity of a nest producing at least one independent young was 72%; however, n est success varied throughout the breeding season, being lowest and most va riable for early- and late-season nests. Based on 98 nests with complete re cords, mean clutch size was 2.23 eggs, 61.2% of nestlings fledged successfu lly, and 48.4% of all eggs laid resulted in independent young. Clutches of three produced the most independent young per breeding attempt in all years . Annual population productivity was enhanced because pairs made more than one nesting attempt per breeding season, either by renesting following an e arly season failure or by producing second broods. Clutch size, probability of nest success, probability of renesting, and number of fledglings produc ed per attempt all declined as the breeding season progressed. Mortality fa ctors included weather, predation, chicks falling out of nests, and vehicle collisions with fledglings. Environmental variability may influence spatia l and temporal variation in timing of reproduction and nesting success of C rested Caracaras in Florida.