Global impacts of climate change on avian functional diversity

Climate change is predicted to drive geographical range shifts, leading to fluctuations in species richness (SR) worldwide. However, the effect of these changes on functional diversity (FD) remains unclear, in part because comprehensive species‐level trait data are generally lacking at global scales. Here, we use morphometric and ecological traits for 8268 bird species to estimate the impact of climate change on avian FD. We show that future bird assemblages are likely to undergo substantial shifts in trait structure, with a magnitude of change greater than predicted from SR alone, and a direction of change varying according to geographical location and trophic guild. For example, our models predict that FD of insect predators will increase at higher latitudes with concurrent losses at mid‐latitudes, whereas FD of seed dispersing birds will fluctuate across the tropics. Our findings highlight the potential for climate change to drive continental‐scale shifts in avian FD with implications for ecosystem function and resilience. Climate change is expected to drive geographical range shifts and fluctuations in species richness worldwide, but the effect of these changes on functional diversity remains unclear. We use morphometric and ecological traits for 8268 bird species to estimate the impact of climate change on avian functional diversity (FD). The results show that climate change is likely to drive continental‐scale shifts in avian FD that differ across trophic niches, with implications for the functioning and resilience of future ecosystems.