Assembleia de aves consumidoras de frutos de sub-bosque em diferentes altitudes em uma área de Mata Atlântica no estado do Rio de Janeiro

Abstract

In this study, we investigated the altitudinal distribution of the species composition, richness and abundance of fruit-consuming birds at five elevations and assess the influence of vegetation structure on bird diversity. The study was conducted at the Reserva Ecológica de Guapiaçu which is adjacent to the Três Picos State Park, Cachoeira de Macacu, RJ. Bird species data were collected during 24 field excursions, including six bimonthly (July/2010 to May/2011) and 18 monthly (July/2011 to Dec./2012) samplings. To sample birds, we used the capture-mark-recapture method with mist nets, exposed for seven hours/day over five elevations along an altitudinal range of 1000 m. The sampling effort was 8400 net hours. The vegetation structure was sampled in three 100 m2 plots adjacent to the mist net lines in each elevation, in which different plant habits densities were measured. We measured the total height and diameter at breast height of trees, saplings and shrubs, and the diameter 50 cm from the ground for bushes. We captured 448 individuals of 35 bird species, distributed in 16 families. Of the birds captured, 26 % are endemic to Atlantic Forest, and four species are categorized with some degree of vulnerability. Sixteen species were classified as frugivorous and 19 as insectivorous-frugivorous. Leptopogon amaurocephalus, Mionectes rufiventris, Lanio melanops, and Chiroxiphia caudata were captured in the five elevations, and the last two were the most abundant species. Elevations of 370 and 770 m supported the highest species richness and abundance. Bird composition differed among the elevations, and 170 and 1000 m were the most distinct. Insectivores-frugivores dominated the understory of the five elevations. Altitudinal displacements were recorded for five species, and the largest displacement performed by an individual was that of Attila rufus, captured at 770 m and recaptured at 370 m. The understory was most dense at the 170, 370 and 1000 m elevations. Bamboos were recorded only at 1000 m, while herbs were limited to lower elevations (170 and 370 m). The vegetation structure differed among elevations as a result of different vegetation type densities and plant heights. Three elevations, 170, 370 and 1000 m, had a dense understory. The latter had a relatively simpler vegetation structure due to the high number of shorter trees, highest number of saplings and presence of bamboo. Bird diversity was sensitive to vegetation structure,and in particular to tree height, which decreased as altitude increased. This relationship between bird diversity and vegetation structure highlights the importance of preserving vegetation structure to maintain the fruit-eating bird diversityin REGUA and PETP