Landscape heterogeneity and diurnal raptor diversity in Honduras: The roleof indigenous shifting cultivation

I studied the relationship between diurnal raptor diversity, density, and r ichness, and landscape heterogeneity in continuous primary forests and fore sts farmed by native Amerindians in the Rio Platano, Biosphere Reserve of n ortheastern Honduras from January to June 1996 and 1997. I estimated landsc ape heterogeneity-the variability in naturally occurring and/or anthropogen ic habitat mosaics-by mapping the extent and distribution of five human-mod ified and natural habitats in 24 1 km(2) survey plots. I used the Shannon i ndex to calculate landscape heterogeneity values for the respective plots b ased on the proportion of total area of each habitat within each plot. Diur nal captor surveys from canopy emergent viewpoints in these plots resulted in 137 observations of 18 species of captors. Four species (Coragyps atratu s, Ictinia plumbea, Leucopternis albicollis, and Buteo magnirostris) differ ed significantly in abundance among heterogeneity classes, Raptor diversity , density, and richness all increased directly with increasing landscape he terogeneity. Landscape heterogeneity was more important in explaining diffe rences in raptor species diversity than the presence or extent of any singl e habitat or combination of habitats. In contrast to previous studies, my r esults indicate the importance of indigenous shifting cultivation in alteri ng the naturally occurring patterns of habitat mosaics in lowland rain fore st and its effect on bird species abundance and diversity in a rain forest ecosystem.