Efeitos da fragmentação florestal sobre a predação de ninhos e comunidades de aves nidificantes da Mata Atlântica do Sudeste do Brasil

Abstract

Habitat loss and the resulting fragmentation are the primary drivers of biodiversity decline in terrestrial ecosystems. Birds respond rapidly to the effects of fragmentation, with changes in diversity, ecology, behavior, and reproduction. Nest predation is the leading cause of mortality in birds and may be intensified in fragmented habitats due to an increase in number or frequencies of generalist predators, which in the absence of top predators may increase in abundance (mesopredator release hypothesis). In this context, this thesis has as its central objective to evaluate the effects of fragmentation on the survival of forest bird nests in tropical environments, being structured in two chapters. The first chapter had as objectives to identify and compare the main nest predators in continuous and fragmented areas of the Atlantic Forest, as well as to test for the first time the mesopredator release hypothesis for a tropical forest. For this, active nests of understory birds were analyzed in one of the main continuous forest tracts of the Atlantic Forest in southeastern Brazil and in adjacent fragments. The nests were monitored in the field by camera traps, which enabled the identification of predators and the modelling of nest survival. Additionally, bird and mammal samplings were carried out to evaluate the assumption that nest predators may be more abundant in fragments due to the rarity of regulating carnivores. The results did not provide support for the tested hypothesis, since the frequencies of regulating carnivores; nest predators and nest survival rates were similar between habitats. The second chapter focused on the breeding activity hypothesis, which predicts a lower number of reproductive species and lower offspring production in fragmented environments. Using active nests as direct evidence of reproduction, nesting species richness was compared, as well as nest frequency and survival between continuous and fragmented habitats. The results did not indicate significant differences in nesting species richness between the environments, although the total frequency of nests and of certain species were higher in the fragments. Overall, the results suggest that in landscapes still relatively preserved, forest fragments may maintain relevant ecological processes and sustain reproductive bird communities. However, this apparent stability is accompanied by changes in community composition, with replacement of more sensitive species by generalist species, which may imply long-term effects on the ecological integrity of these systems.