Abstract
Avian migration has long captured human interest, but the causes of the evolution of migration remain unclear due to limited study of the full spectrum of migratory strategies, including short‐distance and intratropical movements. We examine the climatic drivers of migration across the roughly 1300 species of suboscine birds, a group containing many intratropical migrants. Comparative analyses confirm that migratory behavior in temperate‐breeding suboscines evolves in association with temperature seasonality. The evolution of migration in the tropics, however, has a more complex association with climatic variables including precipitation and greenness seasonality. Projections under future climate scenarios show that suboscines will experience average lower temperature seasonality, potentially favoring the loss of migration, but higher precipitation seasonality, potentially favoring an increase in short‐distance migration. The divergent impacts of climate seasonality on the evolution of different migratory strategies highlight the complexity of climate‐movement associations and the challenges of projecting responses to climate change.
We used comprehensive data on phylogenetics, migratory behavior, and past and future climate to test the climate‐migration associations in a large radiation of roughly 1300 suboscine passerine birds. We demonstrate that while longer‐distance migration is influenced overwhelmingly by seasonal fluctuations in temperature, tropical migrations have more complicated associations with the environment, including precipitation seasonality and fluctuations in vegetation greenness. Our future climate projections (2080–2100) suggest that long‐distance, temperate‐breeding migrants will experience conditions that might reduce migratory propensity on average, while tropical breeders might experience conditions that either increase or reduce migratory propensity.
