The wetland complex lies within the Big Muddy Creek floodplain and consists of Manning Lake and associated wetlands and grasslands. Most of the proposed IBA lies within the Fort Peck Indian Reservation. Because of the wildlife values at the site, the Fort Peck Tribes, U.S. Fish and Wildlife Service, Natural Resources Conservation Service, and Montana Fish, Wildlife & Parks formed the Manning Lake Working Group in 2004 to implement habitat protection and restoration in the area. In 2005, the Working Group received a Tribal Landowner Incentive Program Grant that is being used to help consolidate land ownership and develop a conservation plan to manage the site as a tribal wildlife refuge.
The site supports one of only five breeding colonies of Franklin's Gulls in Montana. Other colonial birds that nest here include Eared Grebe, Forster's Tern, Black Tern, and White-faced Ibis; 1000s of waterfowl also breed here. Breeding shorebird species include Marbled Godwit, Long-billed Curlew, Upland Sandpiper, Willet, and Wilson's Phalarope. Nesting passerines include Sprague's Pipit, Lark Bunting, Grasshopper Sparrow, Baird's Sparrow, Nelson's Sharp-tailed Sparrow, Le Conte's Sparrow, and Chestnut-collared Longspur. Formal surveys for species of Continental and Global significance have not yet been conducted.
A large portion of the area serves as pastureland for area ranchers, and overgrazing is a potential threat. However, because the same families have grazed the area for decades and have practiced sound grazing practices, we feel overgrazing is only a minor threat. Wetland drainage is a potential threat because a number of wetlands have been drained in the northern portion of the IBA. Native prairie within the Big Muddy floodplain north of the IBA has been broken for farming and is a potential threat, especially on the northern portion of the area. Oil and gas development has returned to northeastern Montana. Pollution resulting from leaking containment pits and other infrastructure items associated with oil and gas development are threats to the IBA.
Of the total IBA acreage, 24.9% is in general tribal ownership and 54.9% is tribal allotment; tribally allotted lands are owned by individual tribal members or families. The remaining 20.2% of the IBA is under private ownership by non-tribal members.
The Manning Lake Wetland Complex lies within the Big Muddy Creek floodplain near the confluence with Smoke Creek. It consists of Manning Lake and associated wetlands and grasslands. Wetland habitat consists of open water, depressional wetlands, oxbows, and sedge meadows. Several wetlands have been partially drained by surface ditches. Most of the uplands surrounding the Manning Lake Complex are native mixed-grass prairie. Manning Lake proper is approximately 1,100 acres, of which 200 acres are primarily open water habitat and the remainder is alkali and hardstem bulrush marsh and sedge meadow lying to the north of the open water.
The majority of the IBA lies on the Big Muddy Flood Plain, and a large part of it remains wet into July of most years. The major land uses are grazing and haying, which are very compatible with wildlife and bird nesting as these activities are usually delayed until the ground dries out. The Fort Peck Tribes have designated a portion of the nominated IBA as a Tribal Wildlife Refuge with the intended primary use being wildlife conservation.