Taxonomic and functional responses of bird communities to forest patch configuration in a tropical forest landscape

Abstract Forest fragmentation is a major threat to tropical biodiversity, yet whether changes in forest patch configuration influence taxonomic and functional dimensions of bird communities remains unclear. We investigated how forest patch configuration influences bird community structure in the Guangua–Elala forest of northwestern Ethiopia. Bird communities were surveyed using fixed-radius point counts and classified into feeding guilds, habitat-preference groups, and foraging strata. Forest fragmentation was quantified using patch size, isolation distance, and edge length. Taxonomic diversity was evaluated using alpha- and beta-diversity metrics, whereas functional responses were analysed using negative-binomial generalized linear models. A total of 67 bird species comprising 902 individuals were recorded. Although forest fragmentation variables were not significantly associated with local taxonomic diversity, bird assemblages showed high compositional dissimilarity (βSOR = 0.885), largely driven by species turnover (βSIM = 0.843) rather than nestedness (βSNE = 0.042). Functional composition was more strongly influenced by forest fragmentation than taxonomic diversity. Forest isolation significantly affected feeding-guild responses, whereas patch size influenced foraging-stratum composition. These findings indicate that forest fragmentation restructures bird communities primarily through species replacement and functional restructuring rather than reductions in local taxonomic diversity. Conserving well-connected networks of remnant forest patches will therefore be essential for maintaining both avian biodiversity and ecosystem functioning in fragmented tropical landscapes.