Local Extinctions of Terrestrial Insectivorous Birds in a Fragmented Landscape near Manaus, Brazil

Abstract: We examined the distributions of nine species of terrestrial insectivorous birds in 4- to 14-year-old rainforest fragments north of Manaus, Brazil. We surveyed 11 fragments of 1, 10, and 100 ha, 95 ha of secondary vegetation, and nine continuous forest plots (controls) of 1–100 ha. We augmented standard spot-mapping with extensive playback surveys. The fragments had been sampled with mist nets before isolation, so our results could be compared with the pre-isolation distribution. For the nine species, there were 55 cases of local extinction in the 11 fragments between about 1 year after isolation and the time of our surveys. This corresponds to 74% extinction of the local populations in fragments. These extinctions occurred despite the second-growth connection of some fragments to continuous forest as little as 70 m away. Three apparent colonization events by species not detected before isolation also occurred, but these may also reflect inadequate sampling before isolation. Our comparison of fragments and similar-sized control plots in continuous forest showed an area effect on species richness in both fragments and control plots, but fragments had fewer species than control plots of equal size. In a fragmented Amazonian landscape, the full suite of terrestrial insectivores would persist in the short term only in large fragments ( > 100 ha), although much larger areas are probably necessary for the long-term persistence of their populations.