Distribuição e deslocamento altitudinais de aves na Mata Atlântica, com ênfase em beija-flores.

Abstract

Biodiversity distribution is associated to spatial, environmental and biological factors. These factors influence the biological communities dynamics, generating differences in species distribution and abundance, both locally and regionally, and also creating variation in population processes and in animal movements. Variation in the distribution and structure of bird communities in altitudinal gradients is an example, but, there is no consensus about the pattern of altitudinal distribution for birds, and four different patterns are recognized. In this context, the present thesis intended to evaluate the ecological responses of birds to altitude. In the first chapter, we reviewed the literature to evaluate the state of the art about birds altitudinal movements/migrations. We found 84 studies, most conducted in the Neotropics. In these studies, authors reported 380 species of birds performing some kind of altitudinal migration, with insectivores and nectarivores the main trophic guilds involved. The studies also showed that there is a set of interacting biotic and abiotic factors that can explain altitudinal migration. Movement to higher altitudes can be explained mainly by resource availability and low predation risk, while migration to lower altitudes appears to be related to competition and limited foraging opportunities. In the second chapter, we analyzed the regional distribution of hummingbirds in the Brazilian Atlantic Forest, using distribution maps and information available in the literature. We found variation in hummingbird species composition in relation to altitude, but a set of factors could probably explain this variation. Our results showed that in addition to the altitudinal effect, the spatial component (latitude and longitude) related to environmental variables were also important to evaluate the birds distributions. In the third chapter, we investigated the altitudinal distribution of birds (and hummingbirds) in five altitudes in the Ecological Reserve of Guapiaçu (170 and 370 m) contiguous to the Três Picos State Park (570, 770 and 1000 m), Rio de Janeiro state. Data were collected bimonthly (July/2010 to June/2011) and monthly (August/2011 to July/2012), using a capture-marking-recapture method with mist-nets (12 x 2.5 m, 32 mm mesh) opened in the undergrowth for 7 hours/day in each sampling point. We also collected data on hummingbirds monthly using linear transects (400 m long). We captured 95 bird species (53% endemic to the Atlantic Forest), including 10 hummingbird species (8 endemic). The highest species richness was found at the altitude of 770 m and the lowest species richness was found at the altitude of 170 m. We did not find a relationship between altitude and bird richness. However, we found differences in the composition, richness, abundance and in the trophic organization of birds in the five altitudes, with the altitude of 170 m being different from the others in most cases. For hummingbirds sampled with both methods (captured with mist-nets and observed; 13 species), we did not find differences in the composition and in the richness in all five studied altitudes. Diversity and the higher endemism recorded for the area emphasize the importance of the region for the conservation of the Atlantic Forest birds in Rio de Janeiro state.