eWestern Birds
The Quarterly Journal of Western Field Ornithologists
Occurrence Patterns of Peregrine Falcons on Southeast Farallon Island, California, by Subspecies, Age, and Sex
Sasha Earnheart-Gold, Peter Pyle
ABSTRACT: We summarize observations of 201 Peregrine Falcons (Falco peregrinus) at Southeast Farallon Island during the fall and winter from 1990 to 1999 by age, sex, and subspecies. The northwestern subspecies F. p. pealei and the continental subspecies F. p. anatum occurred with roughly equal frequency. We recorded 10 individuals of the arctic subspecies F. p. tundrius. During fall, adults occurred significantly earlier than immatures. Males tended to occur earlier than females; anatum tended to occur earlier than pealei. Four to six birds per year (of both anatum and pealei) remained through the winter. Under the assumption that wintering individuals returned each year to the maximum extent possible allowed by the observed variation by age, sex, and subspecies, their survival rate was 0.78.