Habitat-related bird community responses in northwest Panay, Philippines

Abstract

The Western Visayas is the most deforested region of the Philippines. The Northwest Panay Peninsula Natural Park, an Important Bird and Biodiversity Area on the island of Panay, is the largest remaining tract of lowland forest in the region supporting a number of bird species of conservation importance. The aim of this study was to quantify the diversity and community composition of bird assemblages across a gradient of habitat disturbance, identifying key species and guilds contributing to habitat-specific community differences and informing conservation management of the park. In 2020, we conducted bird surveys using distance sampling point transects with a 10-minute count period in 4 habitat types: primary forest, secondary forest, plantations, and open areas. We produced measures of taxonomic, species, and functional diversity based on ecological guilds described by diet, body size and feeding stratum, and endemicity, and used generalized linear modeling to investigate the effect of habitat on bird assemblages. We used analysis of similarities to test for differences in community composition across habitats and similarity of percentages to determine what species and guilds contributed to community dissimilarities. We recorded 61 species, including 6 globally threatened species, with the highest and lowest taxonomic and species richness and endemicity in primary forest and open areas, respectively. Primary forest had the largest, positive effect on bird diversity and endemicity, while open habitat had a consistent negative effect. Plantations had a small positive effect on functional diversity only. Community dissimilarities across habitats were largely driven by medium general-level and upper-storey frugivores, small lower-storey insectivores, and small lower-storey and general-level omnivores. Secondary forest and plantations may play an important role in supporting at least some of the primary forest bird community. Our findings emphasize the importance of the site’s primary forest for regional bird conservation, and we provide recommendations for management of this important lowland forest landscape.

Keywords

• anosim
• endemicity
• functional diversity
• glm
• guilds
• panay
• simper
• threatened species