The site comprises sects. 10-15, 22-27, & 34-36 in T12S, R4E, and sects. 7-8, 17-20 & 29-32 in T12S, R5E, Gallatin County. The area takes in the Madison Arm, Grayling Arm, and South Fork Arm of Hebgen Lake plus Horse Butte Peninsula. The three arms of the lake are where wintering Trumpeter Swans concentrate. Most of Hebgen Lake proper is frozen during winter, and the area of open water actually used by the swans typically is much smaller than the 6,475 ha identified as the IBA.
This area supports the largest concentration of wintering Trumpeter Swans in Montana and is among the largest known winter concentrations of Trumpeters in the Rocky Mountains. The Trumpeter Swan is a Level I priority species in the Montana PIF Bird Conservation Plan and is an Audubon Yellow WatchList species. Accordingly, it is a B1 species of Continental conservation concern. The minimum number of individual swans wintering at the site has exceeded the B1 threshold for the species each winter from 2002-2005, and the site qualifies as a Global IBA because of its high concentrations of wintering Trumpeters.
Bison migrate from Yellowstone National Park in winter to Horse Butte peninsula in the center of the proposed IBA. Owing to a controversy over the spread of brucellosis from bison to livestock, in winter the Montana Department of Livestock ?hazes? bison from the area using helicopters, ATVs, and snowmobiles. Buffalo Field Campaign observers have witnessed (and videotaped) more than 300 Trumpeter Swans being driven to flight during helicopter hazing of bison. Continued flushing of wintering swans potentially causes serious energetic stress. Swans also are potentially threatened by recreational disturbance in winter, this threat being smaller than hazing.
Hebgen Lake proper is surrounded by Gallatin National Forest and a smaller amount of private land. The lake is owned by the State of Montana. The private land consists largely of a housing development connected with the town of West Yellowstone, MT.
About 1/3 of the site is a lake that is mostly frozen in winter, with the lower reaches of the arms providing open water that is used by the swans. The surrounding uplands are dominated by coniferous forest, with smaller amounts of sagebrush/grassland on the peninsula.
The national forest lands surrounding the lake are managed for multiple uses that include various recreational activities and some timber harvest and management. The lake proper is also used for various recreational activities such as boating and fishing. Private lands on the peninsula contain houses used year-round.