Age-related differences in abundance and habitat occupation of Steppe Buzzards, Buteo buteo vulpinus, in t

Abstract

Linear densities of Steppe Buzzards, Buteo buteo, were studied along roads at the southernmost edge of the nonbreeding range in the Western Cape Province, South Africa. Adults arrived before first-year birds; peak populations of the former occurred from December to February, and of the latter from January onwards. Except during periods with rapidly changing numbers during arrival and departure, the proportion of first-year birds in three different areas was negatively related to the density of adults. This may be the result of competitive exclusion by adults, or of age-related differences in habitat preference. Adults dominated first-year birds at hunting perches. First-year birds were most frequently found in more closed habitat, where they attempted to kleptoparasitize adults in 18% of all observed instances of prey mantling.