Northern Prairie Wildlife Research Center
246 Cove Lane, Hudson, WI 54016; U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Route 1, Box 96C, Jamestown, ND 58401
Wetlands of the Prairie Pothole Region serve as staging areas for numerous species of arctic-nesting shorebirds during spring migration. In this paper, we address use of basin wetlands by Baird's (Calidris bairdii), white-rumped (Calidris fuscicollis), semipalmated (Calidris pusilla), and pectoral (Calidris melanotos) sandpipers during 1981-84 in Stutsman and Kidder counties of south-central North Dakota. An index to abundance of staging sandpipers varied widely between years and was lowest during wet springs. Peak staging intervals and chronology of migration varied annually for each species, probably reflecting differences among years in foraging conditions and weather encountered prior to arriving in North Dakota. The opportunistic strategy sandpipers employ in their use of prairie wetlands appears to be well-suited to the highly variable water conditions shorebirds encounter during their passage through the region.
The four species of sandpipers acquire fat reserves needed for migration and reproduction while staging in prairie wetlands. The birds maximize fat deposition through intensive foraging during their stay. Time budget analyses indicated foraging occurred during 75-85% of the daylight hours. Dipteran larvae and pupae dominated the diets of all species; both males and females fed principally on chironomids. Each species foraged over a wide range of water depths with larger forms, on average, foraging at deeper sites. Although foraging substrates overlapped, there were characteristic differences between species in microhabitat preferences. White-rumped, semipalmated, and Baird's sandpipers used alkali lakes most; pectoral sandpipers were found primarily in seasonal wetlands. Use of tilled wetlands by all species was relatively low. Pectoral sandpipers, because of their affinity for seasonal wetlands, were most often found in basins located in cropland.
The wetland habitat that historically was available to arctic-nesting shorebirds during their spring and fall migrations through the Prairie Pothole Region has undergone massive change during the past century. We discuss the implications of these changes from the perspective of the needs of migrant shorebirds and consider steps to maintain adequate productive wetland habitat suitable for shorebird use.