Aeroecology drives seasonal movements and predicts future distributions of a critically endangered terrestrial bird

All terrestrial species interact with the airspace.¹ The principles derived from the study of those interactions, i.e., from the field of aeroecology,² are most often used to model species movements (e.g., Miller et al.³ and Nourani et al.⁴). Despite this, they are almost never used to understand species distributions,⁵ an issue fundamental to ecology, conservation, and management.^6,7,8 We used resource selection functions and species distribution models to (1) show that aeroecological principles are a driver of seasonally variable distributions for critically endangered California condors (Gymnogyps californianus) and (2) predict range expansion for this heavily managed and rapidly growing population. Condors used thermal updraft either directly in proportion to, or less frequently than, predicted by its availability. However, during winter, when thermals are weak, they used orographic (deflected) updraft more than would be expected, suggesting that condor distribution was limited by the availability of predictable orographic updraft. Furthermore, resource selection functions for condors always performed better with than without aeroecological predictors. Aeroecological species distribution models predicted that habitat selected most strongly by condors would vary seasonally with changes in the weather, from 1.7%-5.0% (winter) to 6.6%-11.1% (spring/autumn) of California and Oregon. Explaining seasonal variation in condor distribution with aeroecological principles led to insights contrary to conventional wisdom that interannual movement of soaring avian scavengers responds to transiting of their food, domesticated and wild ungulates. Incorporating aeroecological principles into models of species distributions can lead to better understanding of animal movement and distributions and provide information with substantial consequence to endangered species management.