Results
The number of diurnal landbird species that disappeared
from each island ranged from zero (Malawali and Mantanani)
to 15 (Bintan) (Table 1). The percentage of
forest-dwelling birds that disappeared from the islands
ranged from 0% (Balambangan, Malawali, and Mantanani)
to 100% (Mengalum; Table 1). Sampling saturation was
reached for all islands except Mantanani (Fig. 2), and observed
species richness for all islands was very close to
the mean estimated richness (88.7–97.9%; Table 1). Some
species vanished from all the islands where they previously
occurred (Scarlet-rumped Trogon), whereas others
disappeared from some but not all islands (Oriental Pied
Hornbill [Anthracoceros albirostris]) (Supporting Information).
The regression model of percentage of forest cover
explained 34.8% of variation in forest-bird extinctions
across seven islands (Fig. 3). Extinction rate was lower
when forest cover was high (more habitat). Nevertheless,
statistical support for the regression was weak, probably
because our small sample size was small (seven islands).
The relative AICc weight (sums to 1.0) was strongest