Grays Lake lies within the Caribou Range of the in SE Idaho. It is actually a marsh that covers (89 km²; 22,000 acres). Vegetation is primarily hardstem bulrush, cattails and submerged Elodea in the limited amounts of open water. This wetland system provides important habitat for breeding sandhill cranes, trumpeter swans, Franklin's gulls & white-faced ibis. Grays Lake has the largest nesting population of greater sandhill cranes in the world. The refuge's common nesting species of waterfowl include the mallard, cinnamon teal, canvasback, lesser scaup, redhead, and Canada goose.