McCaslin, Hanna – Environmental drivers of avian dispersal

Photo of Hanna holding a nestling adult male kestrel, spring 2017
Hanna holding a nestling adult male kestrel, spring 2017

Dispersal is a critical process for animals because it is the primary method of gene flow between populations, and patterns of dispersal within a species impact genetic structuring and species distributions and abundance. Dispersal is driven by a combination of genetic and environmental factors, and understanding the mechanisms behind dispersal is important to understanding the dynamics of populations, particularly in highly-mobile species like birds. Over the past several decades, climate change has prompted rapid environmental change with widespread effects on many biological systems, but despite evidence that avian dispersal is influenced by environmental conditions and habitat quality, the environmental factors that drive dispersal movements are not well understood. Understanding the interactions between current and future environmental variation and dispersal will be critical to interpreting population trends in a variable environment. I will attempt to address this gap by studying both the environmental factors that affect individual dispersal patterns and the resulting shifts in population distributions.

Photo of an American kestrel, spring 2017
American kestrel, spring 2017

American kestrels (Falco sparverius) are small falcons that occur across a broad range of habitats in North America. Kestrels display a range of different migration and movement strategies throughout North America, and although most disperse only a short distance from their nest site, some individuals disperse very far. I am using bird banding data collected throughout North America over the past 55 years to study patterns of individual dispersal in American kestrels at a large scale, with a particular focus on long-distance dispersal movements. I hope to identify spatial and temporal trends in kestrel dispersal, as well as assess how environmental factors, including temperature, precipitation, and agricultural land development, shape patterns in dispersal. Additionally, I will use breeding bird surveys to study the relationship between changing dispersal patterns and resulting shifts in breeding distributions in American kestrels and other landbirds throughout North America.

Understanding how populations may respond to progressing environmental variation is critical for developing conservation strategies, and understanding how species are currently altering spatial patterns is important for anticipating how future global change may impact species distributions. By assessing birds’ responses to environmental cues, this study will give insight into how birds are able to adjust to the effects of climate change and provide evidence about which parts of their annual cycle are the least flexible and therefore the most important conservation foci.