Landscape for Shorebirds During Migration
The extensive wetlands of the Prairie Pothole Region provide stop over resources for large populations of shorebirds during spring and fall migration. Shorebirds rely on the early availability of food in small, shallow wetlands and on the edges of larger water bodies to continue their journey to the Arctic breeding grounds, or to build up reserves for nesting in the Northern Great Plains and Canada. The vastness of the prairie landscape presents a challenge to scientists studying these birds during spring and fall passage; although some larger areas will have birds year after year, most of the smaller stopover sites change with annual changes in water conditions.
To find solutions that address these problems, scientists at the US Geological Survey, Fort Collins Science Center teamed with HAPET to integrate landscape features into a broad scale migrant shorebird survey across the Dakotas and western Minnesota . The result has provided the first empirical estimates of the number of shorebirds moving through the area, and insight to landscape features sought after by birds during spring and fall migration.
Estimates reveal that 8 million birds stop in the study area during spring migration; 48% of the birds were the small Calidris species, commonly referred to as 'peeps'. For fall, estimates were 8.5 million birds with only 16% peeps (some shorebird species use different routes in spring and fall) . Spring surveys have shown three broad spatial patterns emerging from spatially explicit models predicting shorebird use based on landscape attributes of the percent of grass, density of wetlands, and average slope.
For full results see: Skagen, S.K., D.A. Granfors, and C.P. Melcher. 2008. On determining the significance of ephemeral continental wetlands to North American migratory shorebirds. auk 125:20-29.
View Shorebird Migration Suitability Maps by Species
In addition to providing population estimates, the survey were also useful for modeling and mapping landscape characteristics that are important to shorebirds during migration.
Marbled Godwit, American Avocet, and Willet were strongly associated with a high amount of grass in the landscape.
Wilson's Phalarope and Semipalmated Sandpiper were associated primarily with a large proportion of small, shallow wetlands, and secondly with the amount of grass.
Upland Sandpiper, Dunlin, Hudsonian Godwit, and White-rumped Sandpiper were associated with shallow wetlands, but not with a high amount of grass. The change in distribution of Dunlins between years indicated that inundated cropfields can play an important role in providing stopover habitat during the right climactic conditions.
The apparent differences in high suitability areas for different groups of species indicate that a 'one-size-fits-all' conservation strategy is not appropriate for shorebirds during migration, but neither must conservation strategies be implemented on a species by species basis.
For additional information about grassland birds contact:
Region 7 Inventory and Monitoring Coordinator
U.S. Fish and Wildlife Service
1011 East Tudor Road
Anchorage, AK 99503