Understanding how and why species respond to land-use change is one of the central challenges in conservation biology, yet the causes of variation in the responses of species to land-use change remain unclear. We tested whether adaptation to different abiotic environments influenced the vulnerability of bird communities to agricultural expansion in the Himalayan mountain range, which exhibits a strong east-west gradient in annual temperature variation. We did so by surveying bird communities in forest and agriculture at opposite ends of that gradient. We contrasted metrics of species richness, diversity, community composition, and forest dependency for species across land-use types and regions, and tested whether species’ thermal sensitivity influenced their response to the replacement of forest with agriculture. Agricultural land in the relatively aseasonal east harboured significantly fewer bird species than did forests, a pattern that is starkly reversed in the highly seasonal west. For species common to both regions, eastern populations used forest ~35% more than did western populations. While western species were less constrained by temperature than eastern species, western species with narrow thermal tolerances were also more forest dependent. Selection across a stark environmental gradient on a common species pool appears to have altered the vulnerability of Himalayan birds to forest loss, with communities in the relatively aseasonal east much more sensitive to forest conversion than those in the west. Adaptation to local environmental conditions appears to mediate species' responses to land use change, with thermal specialists more vulnerable to forest loss than species with greater thermal tolerances. Species' responses to global change may differ predictably along abiotic gradients even within a single region or biodiversity hotspot, and such variation must be addressed in conservation planning.