Influence of Patch Size on Bird Assemblages Around the Western Forest Complex of Thailand

Abstract

The effects of patch size of disturbed (secondary) forests were examined on bird assemblages in buffer-zone areas of the Western Forest Complex in Thailand. A sample of 135 line transects (500 m each) was used to determine the occurrence of bird species in 63 forest patches, ranging in size from 4.14 to 9057.01 ha. The data set was analyzed using a simple regression and ordination method based on canonical correspondence analysis (CCA) to create bird assemblage-patch size bi-plots. Ten orders, comprising 23 families and 61 bird species were found, including a Thai endangered species, the Limestone Wren-Babbler Napothera  crispifrons. The results of a simple linear regression showed that the diversity of birds increased as the size of habitat patch increased (R²=0.216; F=16.84; P<0.001). CCA indicated that a patch size of 960.37 ha was the minimum area required to maintain bird diversity. This result suggests that large secondary forest patches are very important in conserving bird assemblages in outer protected areas.

Keywords: forest patches, bird diversity, conservation, buffer zone