Habitat relationships of diurnal raptors at local and landscape scales in southern temperate grasslands of Argentina

PEDRANA, J., ISACCH J. P., BO M. S.

Emu (Austral Ornithology)

CSIRO

Año: 2008 vol. 108 p. 301 - 310

We evaluated the relationship between a diurnal raptor assemblage and local and landscape scales variables in the eastern portion of South America’s temperate grasslands, Argentina (37º32’ to 37º45’S, 57º19’ to 57º26’ W). The landscape is a mosaic of agroecosystems and natural grasslands. Raptor species were sampled with fixed-distance point-count surveys from October 2004 to February 2005. We used generalized additive models to analyze the relationship between raptor occurrence or abundance, and environmental predictors at two spatial scales: local (at plot level: vegetation height and percent-cover) and landscape scale (areas of 25 and 100 Km2 around the survey points). Landscape scale variables included: percentage of each habitat type, landscape diversity, and fractal dimension. Higher values of species richness were recorded in landscapes with a complex matrix of disturbed and undisturbed plots. The abundance of Chimango Caracara (Milvago chimango) was positively associated with roads, sites with a complex matrix of disturbed and undisturbed plots, and high levels of forest cover. The presence of Long-winged Harrier (Circus buffoni ) increased in landscapes dominated by natural habitats, mainly natural grasslands. The presence of Southern Crested Caracara (Caracara plancus) increased mostly in plots with high amounts of short grass cover and away of the roads. Based on our results we suggest that efforts to maintain patches of natural grasslands would be essential for the preservation of ground-nesting species, and second, to preserve habitat diversity would assure that most of the raptor species in the assemblage had their ecological requirements met.