The Use of Terrestrial and Airspace Habitat by Migratory Land Birds during Autumn Migration along a Coastal Ecological Barrier.

摘要

During fall migration, the northern coastline of Lake Superior acts as an ecological barrier for migrating land birds that breed across the boreal forests of Canada and Alaska. This area provides an opportunity to examine the distribution of migrating birds during stopover and active migration in a relatively intact coastal environment. I conducted stopover habitat surveys for birds during two fall migration seasons (Aug-Oct, 2009-2010) and assessed diurnal migratory bird movements during three seasons (Sept - Oct, 2008-2010) within Lake Superior's coastal region of Minnesota, USA.;Land cover and topographic features only weakly explained some migratory species distributions during stopover. Selection of migratory habitats was strongest among permanent resident species. The strongest habitat association for a migratory species was the use of near shore areas and high ridgelines by Swainson's Thrushes. I also detected a difference in the scale of topographic features between long- and short-distance migrants: Neotropical migratory passerines were associated with broad-scale features, while shorter distance migratory passerines were associated with local-scale features. My results suggest that within forested coastal areas, migratory birds are less confined to the shoreline, specific habitat types, or topographic features as reported for other coastal landscapes.;A total of 13,702 raptors and 151,550 non-raptor were recorded using airspace during migration within the coastal region of Lake Superior. Several raptors showed patterns in airspace associated with topographic features such as proximity to the shore and presence of ridgelines. However, the funneling movement that is commonly used to describe raptor behavior along migratory diversion lines occurred only among eagles, suggesting a "leaky" migration funnel for most migratory raptors. In addition, more passerines than raptors showed spatial and temporal structure in airspace distribution, including a funneling movement. I conclude that a) using raptor counts from single migration sites at the "tips" of presumed migration funnels greatly underestimates true numbers of raptors, b) the diurnal spatial and temporal movement patterns of migrating passerines along ecological barriers have been largely overlooked, and c) the airspace associated with anthropogenic development (e.g., buildings, towers, wind turbines) is heavily utilized by both raptors and non-raptors during diurnal migratory periods.