Forest Cover and Edge Effects Drive Bird Functional Homogenization Across Madagascar's (…)

ABSTRACT

Human changes to natural landscapes affect bird species in different ways. Some birds adapt well to new environments, while others see their populations decline or disappear locally. This study aimed to: (1) examine how forest cover and edges affect the richness and specialization of bird communities; (2) explore the link between the ‘winners’ and ‘losers’ of biotic homogenization and whether they are habitat specialists or generalists; and (3) identify which functional traits explain differences between specialists and generalists. We used a bird dataset to calculate the Species Specialization Index (SSI), which measures how many habitats each species uses and places them on a scale from generalists to specialists. The Community Specialization Index (CSI) was calculated using passive acoustic monitoring data from 2019 and 2020. We also gathered functional trait data from AVONET and the IUCN to study their physical and ecological features. Our results show that functional homogenization is happening in Antananarivo. The CSI was higher deeper in the forest and where there was more forest cover, but estimated species richness did not change with these landscape features. There were strong links between the SSI and population trends, with more specialized species more likely to decline. The analysis of functional traits showed that homogenization is not random and can lead to major changes in how bird communities function. These results show that human activities affect specialist and generalist birds differently, leading to non-random functional homogenization.