Avifauna em remanescentes de Mata Atlântica no Sul da Bahia: sensibilidade e conservação

Abstract

The south of Bahia stands out in the conservationist scenario, hosting the largest Atlantic Forest remnants. Consequently, the region has a rich biodiversity, containing taxa that have already been extinct in most of their original distribution. In addition to the great forest remnants, the region includes enclaves of muçunungas, vegetation formations in sandy soils, considered environments sensitive to anthropogenic disturbances. Here we study bird assemblies in the region called Costa do Descobrimento, south of Bahia, between 2011 and 2019, under two perspectives: (i) the influence of landscape changes; (ii) present the first discussed list of muçunungas’avifauna with different structures (grassy-woody - GL and muçununga forest - FM), characterize the use of feelding resources in these formations, as well as the influence of adjacent vegetation formations. In Chapter 1, our hypotheses are (1) native vegetation thresholds of pristine areas be likely to be distinct than sites under long term disturbances and/or more fragmented over a larger chronological scenario for birds; (2) forest dependent (FD) and semi-dependent (FS) species respond differently to patterns of land use; (3) specifical sensitivity patterns are distinct from general patterns studies. We sampled 293-point counts, and 100 were settled across ten different classes of forest cover percentage to generate models for estimating the landscape effects on birds. We defined one buffer (1 km radius) for each point, where we calculated six landscape metrics and three bird attributes. We recorded 340 species; 56 highly sensitive. We confirm that there are higher thresholds in pristine areas; landscapes preserving large remnants of native forest host bird taxa locally extinct from other regions, with many species present only in areas> 60% of native vegetation. This is due to better vegetation structure and a larger set of resources, possibly. Thus, the core area was the variable that showed the highest correlation with the abundance and richness of forest species. We also confirmed that forest FD and FS respond differently to land use; FD species are more sensitive because of their ecological requirements. Our data also revealed specifical patterns of environmental sensitivity. The importance of maintaining 60% thresholds of native vegetation is emphasized, as well as the need to direct efforts to preserve large fragments (≥ 100 ha) in the landscape for the maintenance of more sensitive bird species. In the chapter of muçunungas, in turn, we recorded 216 species; 32 endemics to the Atlantic Forest and 14 threatened with extinction. The most abundant feeding guilds were insectivores (77 species), omnivores (53), and frugivores (32). A total of 109 species were recorded in FM and 183 in GL. Strictly forest birds prevailed in FM (66%), and forest, semi-forest, and open-area species were detected in similar amounts in GL. Similar to restingas, muçunungas are influenced by surrounding environments. There was a predominance of generalist birds, with many species coming from these surrounding environments. Due to the similarities with restingas, it is suggested that similar conservationist strategies could be applied to both environments of the Atlantic Forest.