Genetic Connections: Seasonal Migration and Gene Flow in the Common Loon, Gavia immer.

Common loons, Gavia immer, comprise an interesting species with which to study the genetic link between seasonal migration and gene flow (or breeding site ‘migration’). Common Loons are long-lived, large piscivorous birds that breed in lakes of northern North America and Iceland. Loons are highly philopatric and territorial in breeding areas and also seem to return to the same wintering area. They are subject to multiple threats during all stages of their life (e.g., mercury poisoning, lake acidification, oil spills, botulism). In this study >600 loon samples collected from throughout the range in North America were used to determine population structure using five polymorphic microsatellite loci. Loons breeding near the east coast were strongly differentiated from loons in the rest of the range. Loons west of New Hampshire and Quebec showed a significant level of differentiation. Loons breeding in Wisconsin and New York were genetically distinct from other populations as well. This pattern of genetic differentiation can be partially explained by seasonal migratory routes; birds wintering on the west coast and in the Gulf of Mexico overlap in breeding areas but this may not be true of eastern birds. Understanding population genetic structure and relationships of both wintering and breeding populations will provide information on the impacts of stressors to loon populations. These results may also inform population genetic studies of other migratory birds