Snow cover dynamics: an overlooked yet important feature of winter bird occurrence and abundance across the United States

Snow cover dynamics (i.e. depth, duration and variability) are dominant drivers of ecological processes during winter. For overwintering species, changes gradients in snow may impact survival population (e.g. facilitating via thermal refugia or limiting reduced resource acquisition). However, rarely used species distribution modelling, especially for birds. Currently, we lack understanding how affect bird distributions which functional traits drive these associations at regional continental scales. Using observations from eBird, a global community science network, explored the effects on patterns occurrence counts 150 species. We quantified relative importance, species-specific responses trait-based relationships abundance to ecologically relevant across United States. were important environmental predictors models, ranking within top three most (> 90%) count 79%) contiguous Species exhibited gradient association avoidance, yet birds limited by long, persistent seasons. Duration winter percent frozen ground without structured eastern USA, whereas variability was stronger driver western USA. Birds associated with seasons had greater dispersal capacity dietary diversity, inhabiting regions variable generally habitat generalists. Our results suggest that various filters Global climate change is rapidly degrading key characteristics seasonal cover. A changing cryosphere elicit distributional many birds, potentially accelerating range shifts novel assemblages.