DISTRIBUTION AND ABUNDANCE OF RAPTORS IN PUERTO RICO

摘要

From July 1986 to June 1988, I counted all raptors (Falconiformes and Stri-giformes) seen or heard along 15 8-km routes in the three major life zones of Puerto Rico (moist, wet, and dry). Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) were the most abundant year-round residents. Red-tailed Hawks were more abundant in the moist zone than in the wet zone. American Kestrels did not differ significantly in the dry and moist zones. Red-tailed Hawks were more abundant than American Kestrels in the moist zone. The most abundant winter residents were Merlins (F. colum-barius). Peregrine Falcons (F. peregrinus,) and Ospreys (Pandion haliaetus); all three species were frequently detected in the dry zone but were less abundant than American Kestrels. The abundances of Merlins, Peregrine Falcons, and Ospreys did not differ significantly. The abundances of raptors (pooled) peaked in autumn (September-November) and winter (December-February). Roadside counts were highly variable (coefficients of variation ranged from 85-243%). As a result, the within-year sample-sizes (8-km routes) needed to provide confidence limits of ± 10-50% (t_(0.05) ≈ 2.0) on mean abundance estimates (Y) of the most abundant species in the life zones were high.