The Prairie Pothole Region of the northern Great Plains has been called North America’s duck factory. Most conservation there starts with ducks. So, it makes sense that the region’s landscape–level habitat assessment tools known as thunderstorm maps start with ducks, too. But those maps don’t end with ducks.
The Prairie Pothole Region produces roughly half of all ducks on our continent. However, the region also is vital to some 175 species of non–game birds: grassland birds, wetland birds, raptors and shorebirds. And the ongoing conversion of native grasslands and wetlands to agricultural fields threatens habitat for all avian species. That’s where the thunderstorm maps come in.
The maps link bird survey data and land–cover characteristics developed from satellite imagery to show the population density and distribution of a given bird species over a wide geographical area. The maps have nothing to do with weather. They are so named because their colorful display resembles a Doppler radar image of a thunderstorm. These t–storm maps are an ever more important science–based tool for U.S. Fish and Wildlife Service use in making regional land acquisition decisions.
“Over the years, field staff have done an excellent job of identifying parcels for land acquisition,” says Neal Niemuth, an integrated bird conservation scientist at the Service’s Habitat and Population Evaluation Team (HAPET) office in Bismarck, ND. “However, models and maps give a broader regional perspective than any one person can acquire, and they help inform decisions about which areas give the best return on investment and which areas should be targeted for individual species.”
The t–storm maps, produced by HAPET offices in Bismarck and in Fergus Falls, MN, are part of the evaluation process for acquisition of wetland and grassland easements. The maps’ models could be “an excellent starting point” for various Service landscape conservation efforts, Niemuth says. HAPET satellite offices in Kansas and Montana are already developing t– storm maps for the Flint Hills Legacy Conservation Area in Kansas, the watershed surrounding Bear River Migratory Bird Refuge, UT, and elsewhere.
Waterfowl t–storm maps have existed for two decades. They use Refuge System Four–Square–Mile Survey data as their basis and focus primarily on ducks. Non–game bird t–storm maps are newer. They use North American Breeding Bird Survey or HAPET Shorebird Survey data as their basis, and they pertain to grassland species such as bobolink, chestnut–collared longspur, northern harrier, upland sandpiper and grasshopper sparrow; wetland species such as American bittern, black tern and sora; and shorebirds such as marbled godwit, willet and Wilson’s phalarope.
Niemuth and his colleagues use non–game bird t–storm maps, waterfowl t–storm maps and “decision trees” to help the Service determine where to buy easements from private landowners. Whether the parcel in question is a grassland easement or a wetland easement, the process starts with ducks—more specifically, the density of breeding duck pairs per square mile. If the duck pair density is less than 25, the parcel is disqualified “absent extraordinary justification.” If the duck pair density is greater than 25, the parcel remains in consideration and other factors—such as risk of agricultural conversion, endangered species priority and wetland– or grassland–dependent migratory bird priority—help shape the parcel’s overall acquisition priority.
This modeling gives regional decision makers a sense of the parcel’s conservation value to the Service and its non–game bird trust resources. The process uses science to help demonstrate and predict biological outcomes, Niemuth says. Spatial modeling also adheres to the tenets of strategic habitat conservation (SHC), the Service concept that directs land managers to do business in a way that sets biological goals for priority species populations.
“These are great tools for SHC,” Niemuth says of the maps. “Everyone says they are doing SHC, but these efforts really embody the SHC framework.”
