부산대학교 도서관

Grassland birds are declining as a consequence of habitat modification, and these declines have generated efforts to determine how birds cope with changes in habitat features, especially in agricultural landscapes. The objective of our study was to examine the relationship between grassland birds and vegetation structure in the Northern Campos of Uruguay. Vegetation variables were sampled on 4 sites that differed in agricultural management: (1) 'Crop' site, a combination of annual crops and seeded pastures; (2) 'Pasture' site, seeded pastures only; (3) 'Native 1' site, natural grasslands under sheep and cattle grazing; and (4) 'Native 2' site, natural grasslands grazed by native Pampas deer (Ozotoceros bezoarticus) and cattle. We used multivariate analyses to examine the relationship between bird abundance and vegetation variables. Vegetation structure varied among sites, and most of these differences can be linked to specific management activities typical of each site. Mean vegetation height was greater (and more variable) in cultivated grasslands (Crop and Pasture sites), whereas mean percentage grass contacts (grass cover) was greater in natural grasslands (Native 1 and 2 sites). Vegetation variables accounted for a significant amount of variation in bird distribution and abundance (14.8%). Grassland birds were associated most strongly with vegetation height, grass cover, and vegetation patchiness. Some of the species associated with the highest values for these environmental gradients were Dark-throated Seedeater (Sporophila ruficollis), with vegetation height; Pampas Meadowlark (Sturnella defilippii), with grass cover; and Burrowing Owl (Athene cunicularia), with vegetation patchiness. Unlike facultative species, many grassland-specialist birds were associated with characteristic features (i.e. high grass cover) of natural grasslands used by livestock. Others, however, were associated with typical features (i.e. taller vegetation) of cultivated grasslands. Thus, Pampas grassland bird populations would benefit not only from native-grassland preservation efforts, but also from management guidelines for agriculture-dominated lands. Keywords: agricultural gradient, bird-vegetation associations, Pampas grasslands Las aves de pastizal estan declinando como consecuencia de la modificacion de habitat y es importante entender como las aves enfrentan cambios en las caracteristicas del habitat, especialmente en agroecosistemas. Examinamos la relacion entre aves de pastizal y estructura de la vegetacion en los Campos del Norte de Uruguay. Se muestrearon variables de vegetacion en cuatro sitios con diferentes manejos agropecuarios: (1) 'Cultivo', cultivos anuales y pasturas exoticas; (2) 'Pastura', pasturas exoticas exclusivamente; (3) 'Nativo 1', pastizales nativos pastoreados por ovinos y vacunos, y (4) 'Nativo 2', pastizales nativos pastoreados por Ozotoceros bezoarticus (herbivoro nativo) y vacunos. Utilizamos analisis multivariados para examinar la relacion entre la abundancia de las aves y la vegetacion. La estructura de la vegetacion vario entre sitios y la mayoria de las diferencias pueden ser relacionadas con las actividades de manejo caracteristicas de cada lugar. La altura de vegetacion fue mayor en los pastizales cultivados ('Cultivo' y 'Pastura') mientras que la cobertura de pasto fue mayor en los pastizales naturales (Nativo 1 y 2). Las variables de vegetacion explicaron una parte significativa de la variacion en la distribucion y abundancia de aves (14.8%). Las aves mostraron una asociacion mas fuerte a la altura de la vegetacion, la cobertura de pastos y el parcheado. Algunas de las especies que mostraron las asociaciones mas fuertes fueron Sporophila ruficollis con la altura de vegetacion, Sturnella defilippii con la cobertura de pastos y Athene cunicularia con el parcheado. Muchos especialistas de pastizal estuvieron asociados con caracteristicas tipicas (i.e. alta cobertura de pastos) de los pastizales naturales. Otros, sin embargo, estuvieron asociados con caracteristicas tipicas (i.e. vegetacion alta) de pastizales cultivados. Las aves pampeanas no solo se beneficiarian con la preservacion de pastizales nativos sino tambien con la implementacion de lineamientos de manejo en areas dominadas por la agricultura. Palabras clave: asociaciones aves-vegetacion, gradiente agropecuario, pastizales pampeanos DOI: 10.1650/CONDOR-15-49.1