Date of Award

Spring 5-7-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Brian Olsen

Second Committee Member

Erik Blomberg

Third Committee Member

Brian McGill

Additional Committee Members

Jeffrey Runge

Iain Stenhouse

Abstract

Migratory animals exploit multiple habitats across the extent of their range and conditions experienced can have considerable effects on individual survival and population size. Understanding where species are exposed to survival risks and evolutionary selection pressures and how connected are different portions of the range requires defining a complete annual movement network with all major seasonal sites—e.g., breeding, migratory stopovers, staging, and wintering—and describing where populations may or may not overlap in space and time. I used movement data collected from satellite-tagged Red-throated Loons (Gavia stellata) to provide new and more accurate information about spatial use during the full annual cycle for this species in eastern North America. I examined whether specific behavioral states could be inferred from raw spatiotemporal data, and explored the degree to which environmental cues cause variation in migratory movements, to understand how they will respond to environmental changes in different areas of their migratory corridor. Lastly, I estimated winter home ranges of individual loons and quantified how selection of these areas varied in relation to environmental conditions to better describe important winter habitat for the species within the Mid-Atlantic Bight. Four primary migration routes were used to travel between mid-Atlantic wintering and arctic breeding grounds. The major sites identified as core use areas included lower Hudson Bay and James Bay, the lower Great Lakes, the Gulf of St Lawrence, Nantucket Shoals, and the major bays of the mid-Atlantic region, where birds were captured in winter, including Delaware Bay, Chesapeake Bay, and Pamlico Sound. Individuals differed in their tendency to be intensive versus extensive in their movement behaviors, which corresponded with individual differences in the scale of their use of the landscape. Photoperiod was an important indicator of increased movement at the onset of migration and wind speed was indicative of whether conditions were conducive to migratory flights. Stopover habitat and winter home ranges were associated with warmer, shallow, coastal waters with higher surface current velocities and chlorophyll a concentration. Overall, however, Red-throated Loons exhibited a high degree of individual variation in their movement behavior and responses to environmental conditions.

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