Thesis

Migration patterns of flammulated owls (Psiloscops flammeolus) using light-level geolocators

Flammulated owls (Psiloscops flammeolus) are small nocturnal owls that are thought to migrate long distances every year from summer breeding grounds in the western United States and southern Canada to winter habitat in Mexico. They are cryptic and elusive cavity nesters and little is known about their migratory patterns or winter habitat. They have been named a Species of Concern by the U.S Fish and Wildlife Service be cause of potential habitat destruction. The goal of this research was to track the movements of these owls during their migratory season and over the winter using light-level geolocators, which records ambient light levels that correspond to sunrise and sunset times to determine specific bird locations. During 2012-2013, 60 geolocators were attached to male and female flammulated owls in breeding sites in Washington, Colorado, Utah, and California. In 2013-2014, 16 of these geolocators were recovered from birds in California, Utah, and Colorado. The migratory routes of these birds were analyzed using GIS and further analysis was performed to determine habitat characteristics of their winter home ranges in Mexico. Consistencies in migratory routes and wintering areas between owls from different breeding locations contributed to greater knowledge about the migratory ecology of this owl. Novel results for the migratory behavior of a mated pair from California who used comparable routes and wintering areas before returning to breed together the following year, as well as a female owl from Utah with multiple years of data that showed her using a very similar route and wintering area between years also provided new information that was not yet confirmed about female flammulated owls. This geolocator analysis along with additional research on habitat preferences of flammulated owls in California is the first step in assessing the current status of this species with the goal of a broader western U.S. effort in the future.

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