Abstract
Bird communities were studied in two types of fragmented habitat of Atlantic forest in the State of Paraná, southern Brazil; one consisted of forest fragments that were created as a result of human activities (forest remnants), the other consisted of a set of naturally occurring forest fragments (forest patches). Using quantitative data obtained by the point counts method in 3 forest patches and 3 forest remnants during one year, species richness and relative abundance were compared in those habitats, considering species groups according to their general feeding habits. Insectivores, omnivores, and frugivores presented similar general tendencies in both habitats (decrease of species number with decreasing size and increasing isolation of forest fragment). However, these tendencies were different, when considering the relative abundance data: the trunk insectivores presented the highest value in the smallest patch while the lowest relative abundance was in the smallest remnant. In the naturally fragmented landscape, time permitted that the loss of some species of trunk insectivores be compensated for the increase in abundance of other species. In contrast, the remnants essentially represented newly formed islands that are not yet at equilibrium and where future species losses would make them similar to the patches.
Highlights
The impressive biological diversity of tropical forests is seriously threatened by rapid and continuous deforestation
Species richness and relative abundance data on bird communities were obtained using the point counts method in two kinds of fragmented habitats in Paraná State, southern Brazil: one consisted of forest fragments that were created as a result of human activities, and the other consisted of a set of naturally occurring forest fragments
The relative abundance of trunk insectivores was highest in the smallest patch, but lowest in the smallest remnant; the high relative abundance in the smallest patch is due to the increased abundance of some species of that guild (Fig. 3)
Summary
The impressive biological diversity of tropical forests is seriously threatened by rapid and continuous deforestation. Species that benefit from forest fragmentation tend to increase their relative abundance in the smallest and more isolated forest fragments principally due to (1) the increase in area of their habitats, as for edge species (Laurance et al 1997), The field method of point counts is commonly used around the world for studies on species richness and relative abundance of birds. The point counts method is essentially counting birds at previously determined points. Such counts are made based on birds seen and heard during a fixed period of time. The first published work carried out in Brazil on the bird community using point counts was done in the interior of São Paulo State (Vielliard and Silva 1990). There are still only 16 papers using point counts published in Brazil, mostly in the States of São Paulo and Paraná, additional unpublished results of academic theses exist
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