Efeitos da insularização sobre guildas de aves em ilhas do reservatório da UHE Balbina na Amazônia brasileira

Abstract

One of the more intense anthropogenic environmental changes on ecosystems is habitat fragmentation, which is identified as a major threat to biodiversity throughout the world. In the Amazon forest wide areas are also transformed in fragmented landscapes, which remnants are isolated by different types of environments. Although the formation of the reservoirs of hydroelectric plants is an important factor of forest fragmentation in the Amazon, there are few studies devoted to the subject in the region. Deleterious effects of forest fragmentation on bird communities in particular have been observed in Neotropical rainforests studies, indicating that the water matrix surrounding forest fragments may be an important barrier to species occupation in these remaining. This study aimed to evaluate the effects of fragmentation on the basis of metric space on some local guilds of birds on 27 islands of about 3500 formed in the hydroelectric reservoir of Balbina. The islands, selected by similarity in vegetation structure, have areas between 4.7 to 1815 ha and different levels of isolation from other islands, and areas of continuous forest surrounding the reservoir. I sampled 172 points by auditive census and playback methods, being 142 in islands and 30 in areas of continuous forest. The area and isolation of the islands were directly related to species richness and abundance of studied birds, and the most affected guilds by insularization were insectivorous and soil omnivorous. Of the 55 studied species, 39 might have their chances of occupancy estimated for the study area according to the metrics. There was a lower richness and abundance in sub-sets of islands grouped by area compared to samples in continuous forest. In general, sub-sets of islands had similar richness and abundance on the single islands of similar size.