Habitat relationships of diurnal raptors at local and landscape scales in southern temperate grasslands of Argentina
Julieta Pedrana A D , Juan Pablo Isacch B and María Susana Bó CA Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Centro de Investigaciones de Puerto Deseado, Universidad Nacional de la Patagonia Austral, PO Box 238, Avenuenida Prefectura Naval S/N, 9050 Puerto Deseado, Santa Cruz, Argentina.
B CONICET, Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Funes 3350, (B 7602 AYJ) Mar del Plata, Argentina.
C Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Funes 3350, (B 7602 AYJ) Mar del Plata, Argentina.
D Corresponding author. Email: jpedrana@yahoo.com.ar
Emu 108(4) 301-310 https://doi.org/10.1071/MU07075
Submitted: 12 December 2007 Accepted: 25 August 2008 Published: 27 November 2008
Abstract
We evaluated the relationship between an assemblage of diurnal raptors and local- and landscape-scale habitat variables in the eastern portion of South America’s temperate grasslands in Argentina (37°32′–37°45′S, 57°19′–57°26′W). The landscape is a mosaic of agroecosystems and natural grasslands. Raptor species were sampled using fixed-distance point-counts, from October 2004 to February 2005. We used generalised additive models to analyse the relationship between raptor occurrence or abundance and environmental predictors at two spatial scales: local (at plot level) and landscape (areas of 25 and 100 km2 around the survey points). At local scales we measured vegetation height and percentage cover. 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 from roads. Based on our results, we suggest that maintenance patches of natural grassland is essential for the preservation of ground-nesting species, and preservation of habitat diversity would ensure that most of the raptor species in the assemblage had their ecological requirements met.
Additional keywords: generalised additive models, raptor assemblage.
Acknowledgements
We thank E. Madrid, G. García, L. Biondi, A. Baladrón, A. Cardoni, A. Villegas and P. Percivalle for field assistance; J. Bustamante, A. Rodríguez-Blanco, A. Travaini and J. Zanón Martínez for helping us with the statistical analyses; M. I. Bellocq, Marco Restani and Jianguo Wu for their comments and constructive criticism leading to improvement of this manuscript; F. Isla for providing the image-processing software Idrisi 32; and the Comisión Nacional de Actividades Espaciales, Argentina (CONAE) and D. A. Gagliardini for providing us with the satellite imagery. We appreciate the improvements in English usage made by Jeff Lusk, through the Association of Field Ornithologists’ program of editorial assistance. This work was supported with funds from the Universidad Nacional de Mar del Plata and CONICET, Argentina.
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