Boom and Bust Cycles and Wildlife: The relative abundance of species and specific food and cover resources used by animals vary with the long-term dynamics of flooding and drying in the wetland basin and grasslands of the Refuge. Over 200 bird species from 12 different taxonomic orders have been documented on the Refuge during various seasons.
Breeding Bird Species During Boom (Wet Years) Cycle: Common breeding birds using the Refuge during boom years (wet years) include: eared grebe, mallard, northern pintail, gadwall, blue-winged teal, cinnamon teal, American wigeon, northern shoveler, redhead, lesser scaup, ruddy duck, Canada goose, American Coot, American avocet, Wilson’s phalarope, marbled godwit, willet, Franklin’s gull, white-faced ibis, black tern, common tern, Forester’s tern, and black-necked stilt.
During these wetter periods of long-term precipitation and flooding cycles, many waterfowl, shorebirds, wading birds, gulls, terns, and other wetland-dependent species are present and production is high.
Vegetation and invertebrate communities, as well as nutrient cycling, change when wetlands dry, re-flood, reach the peak flooding extent, and then begin drying again. Aquatic invertebrates reach peak abundance and biomass during wet periods of long-term water cycles in wetlands and include a rich diversity available to many wildlife species.
Wildlife Species During Bust (Dry Years) Cycle: During dry periods of the long-term hydrological cycle, fewer waterbirds breed at the Refuge and the smaller more concentrated and ephemeral nature of summer water reduces nesting attempts and success.
During drier periods, extensive mudflat areas are available as surface water evaporates and recedes to deeper depressions. These mudflats attract large numbers of shorebirds that utilize the rich benthic and terrestrial invertebrate resources. Drying wetlands concentrate aquatic prey for wading birds, and mammals utilizing the wetland basin.
The Refuge is home to many grassland birds throughout the boom and bust cycle. The Refuge has nearly 6,000 acres of intact, northern mixed-grass prairie. Grassland birds are one of the most imperiled groups of migratory birds in North America having experienced steeper, more consistent and more widespread population declines than any other avian guild. The native grasslands of the Refuge provide breeding habitat for Sprague’s Pipits, ferruginous hawk, upland sandpipers, long-billed curlew, marbled godwit, burrowing owl, short-eared owl, grasshopper sparrow, chestnut-collared longspur, Baird’s sparrow, sharp-tailed grouse, and bobolink.
Something for Everyone: Waterbird use on the Refuge is highest during fall and spring migration periods both in wet and dry periods. As more of the basin is flooded in both the spring and fall, critical migration habitat is provided as stopover areas for waterfowl, shorebirds, wading birds, and other species of birds of prey, songbirds, rails, and blackbirds.
Over 6,000 acres of intact, northern mixed-grass prairie provide annual habitat for grassland birds for fall and spring migration and breeding.
Mammal species diversity and abundance on the Refuge is tied to wet and dry cycles. The relative abundance and productivity of wetland-dependent species like muskrat and mink tracks along with long-term hydrological and vegetative dynamics. Many mammal species use the uplands such as coyote, American badger, porcupine, white-tailed deer, mule deer, and pronghorn as they move into the area for forage and breeding.