Responses of avian assemblages to a natural edge in a Chaco semiarid forest in Argentina

J. LOPEZ DE CASENAVE; J. P. PELOTTO; S. M. CAZIANI; M. MERMOZ; J. PROTOMASTRO

AUK

American Ornithologists' Union

Año: 1998 vol. 115 p. 425 - 435

0004-8038

We assessed differences in breeding bird assemblages and vegetation structure between a natural forest edge and the adjacent forest interior in an old-growth Chaco forest of Argentina. The edge had a dense cover of thin stems at low heights and high species richness of woody plants, whereas the interior had high canopy cover, high tree density, high density of thick stems and a more heterogeneous vertical profile. Mist-net and point count surveys were used to sample bird assemblages. We captured 374 birds during 3,553 mist-net hours, and detected 826 individuals during point counts. Overall, we recorded a total of 74 bird species. Bird species richness and bird abundance appeared to be higher in the edge, although differences between habitats were not entirely consistent for mist-net and point count data. Several early-successional bird species were closely associated with edge, and other species occurred exclusively in the interior of the forest. At the guild level, frugivores, terrestrial granivores, arboreal granivores, terrestrial insectivores, and long-flight insect-hunters were more abundant at edge than in interior, whereas the reverse was true for bark insectivores and short-flight insectivores. These results indicate that both edge and interior assemblages are different. The distribution of birds between both habitats appeared to reflect constraints imposed by vegetation structure on habitat use, and could be also related to a differential distribution of food resources, especially fruit.