Established in 1942, Halfbreed Lake National Wildlife Refuge is part of the Big Lake Complex, a large closed watershed with Halfbreed Lake in the center. Initially managed as a flowage and no-hunting refuge easement, it now consists of a mix of federal (76% of site), state (15%), and private (9%) lands, all of which is under the original refuge easment. When wet, the lake provides highly productive breeding and staging habitat for waterfowl and shorebirds.
Yellowstone Valley Audubon volunteers have identified more than 100 species of birds on the refuge. When water conditions are suitable, large numbers of migratory waterfowl (>20,000) and shorebirds (>5,000) use the lake and shoreline. In addition, up to 3,000 Franklin's Gulls have been observed during the post-breeding season in late summer.
The biggest threat facing the refuge currently is drought. The lake has been without appreciable water since August 1998, and it has been virtually unused by wetland birds for most of the year during this drought period. Brown-headed Cowbirds occur on the refuge, although the incidence of nest parasitism on the local native passerines is unknown. The prairie habitat on the refuge is in relatively good shape, but invasive exotic plants occur throughout the basin.
The refuge initially was managed as a flowage and no-hunting refuge easement. In 1987, 3,246 acres were purchased by the Fish and Wildlife Service (FWS) in fee title, which included most of the original easement. The refuge now includes 3,246 acres in fee title, 640 acres of state land (where FWS has acquired the grazing lease), and 400 acres of private land that are covered by the original refuge easement.
The lakebed occupies about 25% of the refuge. Native prairie dominated by western wheatgrass and prairie junegrass constitutes about 70% of the site, with the remaining 5% consisting of greasewood shrublands with a grassy understory.