Forest cover positively affects the occurrence of understory insectivorous Passeriformes in bird communities of the Atlantic Forest

Abstract

Understory insectivorous Passeriformes are known for their vulnerability to forest loss and degradation. Here we investigated whether the proportion of groups of understory insectivorous Passeriformes with different levels of specialization increase with forest cover in the Atlantic Forest, Brazil. We hypothesized that Tyrannides, a very large clade of the order Passeriformes which are closely associated with forest habitat, would be more associated to forest loss than Passeri. We evaluated whether the abundance of single species is associated to forest cover. Published databases were used to select 34 locations and to classify bird species into 3 groups according to degree of specialization in diet and the use of understory for foraging. The percentage of forest cover in 500 meters radii around the locations was calculated and its relationship with the proportion of species was evaluated using binomial models. A total of 86 species of forest Passeriformes was classified as understory insectivores (68 Tyrannides and 18 Passeri). Forest cover was positively associated to the proportion of Passeriformes overall. But while forest cover was also positively associated to the proportion of two more specialized understory insectivores, it had no relation with the group of generalists. Tyrannides were also similarly associated to forest cover. Only some of the most common insectivores Passeriformes had a positive association of their abundance with the forest cover. Higher percentage of understory insectivores in bird communities of Atlantic Forest could be considered indication of higher forest cover.