Effects of changing snow conditions on an iconic raptor of the GYE: the Great Gray Owl

Speaker: Katherine Gura, Colorado State University
Time: Thursday, August 1, 5:30pm MT, talk begins at 6:30pm MT
Location: UW-NPS Research Station at the AMK Ranch, in the Berol Lodge

Abstract
Movement is a key mechanism by which animals respond adaptively to environmental change. However, knowledge gaps persist related to behavioral and fitness responses to climatic stressors. In particular, how changing snow conditions affect wildlife remains poorly understood, despite the key role that snow plays in ecological processes. Indeed, snow conditions are changing rapidly under altered climate regimes, with most temperate, subarctic, and arctic regions of the world experiencing declines in the extent, duration, and depth of snow. We evaluated whether variable winter snow conditions influenced the movements and reproductive performance of Great Gray Owls (Strix nebulosa) in the Greater Yellowstone Ecosystem (GYE) between 2017–2022. We hypothesized that conditions that restrict owls’ access to subnivean prey prompt movement responses and negatively affect breeding. We evaluated habitat selection, long-distance migratory movements, and reproductive output in response to snow depths and wind and ice crusts. Owls proximately avoided deeper snow and more severe wind crusts. Probability of migration increased with more persistent ice crusts (caused by rain-on-snow and melt-freeze events). In the GYE, wind crusts are locally spatially heterogeneous, whereas ice crusts can affect broader areas. Owls therefore appear to be behaviorally plastic, adopting different movement strategies depending on the spatial scale and duration of limiting conditions. Winter snow crust conditions carried over to influence subsequent breeding, although direction of fitness responses differed for wind versus ice crusts. Our findings have implications for understanding vulnerability to climate change, which is occurring at unprecedented rates and scales.

Speaker Bio
Katherine Gura is a research scientist at Colorado State University and a research associate at Teton Raptor Center. Her research focuses on the ecological effects of environmental change, including how wildlife respond to changing snow conditions. She has conducted research in the Greater Yellowstone Ecosystem (GYE) since 2009, primarily on avian ecology. She earned her PhD in Ecology from the University of Wyoming, and her dissertation focused on the factors influencing facultative movements and breeding by Great Gray Owls in the GYE.