BIRD COMMUNITIES IN NATURAL FOREST PATCHES IN SOUTHERN BRAZIL

Abstract

Avifaunal composition was evaluated for natural (not artificial) patches of mixed temperate rain forest in the Campos Gerais region, Parana State, southern Brazil. A large patch (840 ha) and 11 smaller patches (0.5-40 ha) were censused from September to December of 1995 (five hours per month, each site). The total species number was strongly correlated with patch size (I = 0.92, P < 0.001). However, the number of edge species increased with decreasing patch area; the opposite happened with forest species. Thus, the ratio of edge to forest species increased with decreasing patch area. The number of leaf insectivore species decreased the most with a decrease in area. The mean Simpson similarity index was 73.8% among forest patches of similar size. Smaller forest patches linked to the 840 ha patch were more similar to this larger patch than isolated patches. Point counts from January to December 1991 in four patches (72 points each area) showed that several species, specially trunk (and twig) insectivores and omnivores, increased in relative abundance with decreases in area of the patch (density compensation). The habitat appropriation hypothesis, the expansion of niches to include slightly different habitats, could explain the increased relative abundance of two trunk (and twig) insec-