Radar Analysis of Fall Bird Migration Stopover Sites in the Northeastern U.S.
Funding: USGS Science Support Partnership Program
Collaborators: Deanna Dawson, USGS Patuxent Wildlife Research Center
The national network of weather surveillance radars (WSR-88D/NEXRAD) detects birds in flight, and has proven to be a useful remote-sensing tool for ornithological study. We used data collected during Fall 2008 and 2009 by 16 WSR-88D and 3 terminal Doppler weather radars in the northeastern U.S. (U.S. Fish and Wildlife Service Region 5) to study the spatial distribution of landbirds shortly after they leave daytime stopover sites to embark on nocturnal migratory flights. The aerial density of birds, as estimated by radar reflectivity, was georeferenced to the approximate locations on the ground from which birds emerged. We classified bird stopover use by the magnitude and variation of radar reflectivity across nights; areas were considered ‘important’ stopover sites from a conservation perspective if relative bird density was consistently or occasionally high. These results were used to develop models to predict potentially important stopover sites in portions of the region not sampled by the radars, based on land cover, ground elevation, and geographic location. Locally important stopover sites generally were associated with deciduous forests embedded within landscapes dominated by developed or agricultural lands, or near the shores of major water bodies. Large areas of regionally important stopover sites were located along the coastlines of Long Island Sound, throughout the Delmarva Peninsula, in areas surrounding Baltimore and Washington, along the western edge of the Adirondack Mountains, and within the Appalachian Mountains of southwestern Virginia and West Virginia. Important stopover sites, both within and outside radar-sampled areas and on 34 national wildlife refuges sampled by the radars, were mapped in a Geographic Information System, providing base maps for conservation uses and a sampling frame for field surveys to ‘ground truth’ the radar and analytical results. Our analysis indicates that preserving patches of natural habitat, particularly deciduous forests, in developed or agricultural landscapes and along major coastlines should be a priority for conservation plans addressing the stopover requirements of migratory landbirds in the northeastern U.S.
Here’s the full report!