Distribution patterns of diurnal raptors in open and forested habitats in south-eastern Brazil and the effects of urbanization

Abstract

Diurnal raptors may be highly sensitive to anthropogenic disturbances. We evaluated the diversity and abundance of diurnal raptors at an Atlantic Forest-cerrado transition zone in relation to two habitat types (forest fragments and open habitats) and to urbanization, comparing natural open and forested habitats with corresponding habitats within a large urban area. We sampled 80 points, 20 in each of four habitats (semi-natural and urban forests, semi-natural and urban open areas), during 12 months. Diurnal raptors recorded (21 species) included only three out of 10 species with some level of threat in the region. Forested habitats had more species (17) than open habitats (12). Urban areas had only 14 (67%) species, whereas semi-natural areas had all 21 species. Diurnal raptors were as abundant in urban areas as in semi-natural areas in spite of a loss in species richness in urban areas. A re-analysis without Caracara plancus showed that urban areas had a lower mean number of individuals per point than semi-natural areas. Overall species richness usually fluctuated from 14 to 16 species, being slightly higher between January and May than in other months. Overall abundance of diurnal raptors was much higher during summer than during winter. Local extinction may have already occurred for some species of diurnal raptors in the region and will probably shortly include several others. At least C. plancus, a habitat generalist, requires further studies and eventually management actions, since it is able to reach high population numbers in urbanized areas. Furthermore, highly sensitive species that were not recorded require further investigation regarding their conservation status. © 2007 BirdLife International.