Dieta de aves insetívoras terrestres e a disponibilidade de presas em fragmentos florestais amazônicos.

Abstract

Terrestrial insectivorous birds seem to be the most vulnerable avian guild to tropical forest fragmentation; nevertheless, some species in this group can persist in forest remnants and second growth areas. If sensitivity to forest fragmentation could be associated with diet, thus we expected that species with relatively flexible diet be the ones most likely to persist in forest remnants. This study compared diet overlap, niche breath, prey size, and diet variability in two pairs of sympatric species of terrestrial insectivorous birds, each pair containing one species that persists in small forest fragments and one that does not: Myrmeciza ferruginea and Sclerurus rufigularis, and Formicarius colma and Formicarius analis, respectively. Prey availability in forest fragments was also sampled and compared with availability in continuous forests. The species pair, with similar weight, has diet more overlapped. Niche breath indices did not differ between pair members, and diet variability differed in the opposite direction from that hypothesised. Although the two bird species most vulnerable to forest fragmentation fed on larger prey than less sensitive species, prey availability, including that based on prey size, did not differ among fragmented versus continuous forest sites. Thus, diet per se appears not to be an important cause of extinction-proneness in these species. The simplest explanation proposed, that vulnerability to fragmentation is directly related to territory size, requires testing. However, it is consistent with unpublished observations that the bird species feeding on larger prey have larger territories.