Abstract

We characterize the bird assemblage of an isolated relict temperate rainforest (Santa Inés) in terms of its structure, composition and dynamics. The relict character and long-term isolation of this forest remnant, immersed in a matrix of semiarid scrub, provide a natural experiment to assess the consequences of long-term isolation and forest area reduction for temperate bird species. Bird surveys were conducted in a forest fragment and the surrounding scrub matrix between April 1999 (austral autumn) and October 2000 (austral spring) on a seasonal basis. Within the forest fragment we distinguished two microhabitat types: creeks and areas far from creeks (i.e. slopes). A total of 36 species were recorded in the study site, of which 21 were inside the relict forest. Highest bird abundance and richness were recorded during winter and spring, and these were always higher in creek plots rather than slope plots. Comparisons between this assemblage and those distributed in the continuous temperate forest (located more than 900 km southwards) indicate that this bird assemblage shares more similarities, with regard to bird species composition, to southern temperate forest localities and to other relict forests, than to nearer scrub habitats. However, there are eight species, endemic to temperate forests in southern South America, missing from our system. In this regard, our analyses indicate that these eight endemic species should be of great conservation concern and will likely be the ones that will go extinct first if the fragmentation of the temperate forest continues.