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The Effect of Broad-Scale Habitat Condition on the Location and Quality of Migratory Bird Pathways Roger Tankersley, Jr. Tennessee Valley Authority Kenneth H. Orvis University of Tennessee, Knoxville

Migration --Seasonal movement from one region to another by chance, instinct, or plan Long Distance Migratory Birds --Avian species whose breeding and wintering habitats are separated by more than 20 degrees latitude Neotropical Migratory Birds --Birds that migrate between nearctic breeding grounds and neotropic wintering grounds

Base Landcover Available Habitats

Habitat Condition Results: Forest fragmentation and density influence habitat selection during migration, especially for long-distance forest migrants. Long-distance forest migrants appear to select relatively unfragmented, dense forest areas with simple patch boundaries and little coniferous canopy. They avoid heavily disturbed areas with high road densities and a high percentage of agriculture in the surrounding landscape. These species appear to effectively sample widely separated habitats en-route, suggesting that inherited genetic cues for migratory pathways and habitat selection play an important role in stopover selection.

--Habitat Spatial Distribution is key --Orientation: Stellar compass, magnetic compass, olfactory navigation, infrasound. Probably inherited, and likely a constant direction. Species composed of many individuals migrating in slightly different ways. --Nightly Flight Distance: Largely determined by morphology--body size, wing shape, musculature. Re-fueling determines available energy. Models of Migration Pathways

Local Forest Density Percent Agriculture Road Density Integrated Habitat

Broad Front vs. Directed Migration --Broad front migration = no significant impact from removing one stopover --Direct migration = possible significant impact to particular breeding populations

HabitatPathways Application to ReVA

Other Applications and Future Research: --Future scenarios based on landcover change --Climate Change --Environmental assessment tool for Windmills and other vertical obstructions

Mahalanobis Distance Habitat Modeling --More robust models --Based on “Ideal” habitat conditions --Can be used as a probability of survivorship

Possible Climate Change Effects --Likely to have shifting species distributions --Likely to become asynchronous with leaf-out and insects --Modern habitat landscape makes it difficult for species to adapt quickly enough

Assessing Environmental Impact of Windmills --Windmills abundant in western U.S. --Many projects planned in the east --Bird impacts may be significant Project goals: --Examine overlap between quality wind sites and migratory corridors --Create environmental decision tool that incorporates avian considerations early in the decision process

ACKNOWLEDGEMENTS Funded by EPA Regional Vulnerability Assessment program, through an interagency agreement with TVA. Volunteer birders who sampled 128 patches. Statistical help and reading of early manuscripts. Pathways modeling available in Conservation Ecology