Out of the forest: the movements and habitat selection of mixed-species bird flocks in agricultural landscapes adjacent to protected areas in Sri Lanka.

backgroundThe conservation of tropical biodiversity will require not only protected areas, but also strategies to retain animals in degraded secondary forests and countryside agricultural landscapes. This study aims to identify key landscape elements and land-use types that support the movement of mixed-species bird flocks in areas outside, but adjacent to, rainforests in lowland Sri Lanka.

methodsWe recorded flock movement pathways at five sites using handheld GPS, and documented flock composition, land-use, and habitat variables at waypoints every 15 min. Land cover was assessed through high-resolution satellite images, and classified into land-use categories based on dominant vegetation. To analyze habitat selection, we employed a resource selection function using generalized linear mixed models.

resultsA total of 112 flocks were observed, yielding 754 location records (average 7 ± 3 [SD] points per flock) across ten 3-km transects over two years. Overall, a diverse array of species (n = 66) was recorded in flocks. An interaction between land-use and time of day affected flock habitat selection, with preference for water-associated habitat such as marsh and riparian corridors, and mixed cultivation, particularly high after morning, while tea plantations were generally avoided throughout the day. Flock speed was inversely related with land-use preference, and increased when the leading species Orange-Billed Babbler (Argya rufescens) was present. Flock size and species richness strongly declined with increasing distance to the forest, with the exception that marsh, riparian corridors and mixed cultivation retained large flocks.

conclusionsThe findings emphasize how mixed-species flocks can move through human modified landscapes and how their organization (e.g., leading species) influences that process. To sustain avian diversity in agroecosystems, conservation strategies must be spatiotemporally explicit. The study highlights the importance of planning heterogeneous landscapes, including water-associated habitat and mixed cultivations, in order for flocks to persist in this agricultural landscape.