Within-territory use of different land cover types by tropical forest birds in a fragmented landscape

Abstract

Many terrestrial species of birds have been observed to depend on large contiguous areas of forest; in the tropics this appears to be especially true for terrestrial insectivores. Far less is understood about how more-common species, that are less dependent on interior forests, use both forested and non-forested habitat in fragmented landscapes. Using both behavioral observations and radio-tracking relocation data, I quantified the within-territory use of different land cover types for three tropical songbird species, the dusky antbird (Cercomacra tyrannina), red-throated ant-tanager (Habia fuscicauda), and cocoa woodcreeper (Xiphorhynchus susurrans). Small forest fragments (<50ha) were also surveyed for these same species. Territories of all three species were mostly forest (>75%), with different amounts of non-forested land cover. As predicted, all three species had increased use in forest cover and decreased use where neighboring territories overlapped. In addition all three species had higher use of areas where there were more forest gaps and/or ‘soft edges’ in the vicinity. Dusky antbirds were less likely to use monocultures of non-native grass and impervious surfaces, while the other two species had mixed responses to non-forested habitats. Dusky antbirds and cocoa woodcreepers were observed foraging at higher-than-expected frequencies along ‘hard edges’ of forested habitat. All three species were found in forest fragments even smaller than a minimal home range area estimate. Conservation of more-common bird species in fragmented landscapes can include secondary forests and small remnants but for these three species non-forested land cover alone would not be expected to provide breeding habitat.