Sterling WMA is comprised of 1500 acres of wetlands (cattails, bulrushes, and open water), 1550 acres of sagebrush/grass uplands, and 350 acres of agricultural land (corn, grain, and alfalfa). Ownership is a mixture of Idaho Department of Fish and Game (57%), Bureau of Reclamation (40%), and Bureau of Land Management (3%). All of the acres are managed by IDFG as a waterfowl production area.
Sterling WMA supports over 100 species of birds throughout the year. Wetlands and ponds are used by wintering and migrating Trumpeter Swans. Large concentrations of waterfowl are present year-round, as well as migrating shorebirds and breeding marshbirds.
Drought has lowered water levels in some ponds and decreased quality of understory vegetation. Canada thistle, Hoary cress, and perennial pepperweed are the main noxious weeds found at Sterling WMA. Feral cats, magpies, and skunks also seem to have some impact on ground-nesting birds. Integrated Pest Management is therefore on-going. Chemical, mechanical, and biological measures have been used for noxious plants and a trapper is hired to remove mammalian predators around waterfowl nesting season. Russian olive trees have been removed and are being prevented from re-invading.
Sterling WMA consists of low-rolling, loess-covered lava reefs. Uplands are sagebrush/grass types with intermingled wetlands. These wetlands range from open water ponds, to tall emergent zones and sedge meadows. The Russian olive infestations have been significantly reduced through cutting and spraying. The available water is supplemented by leaking canals and run-off from surrounding irrigation. Natural water is from springs and the high water table. The elevation is 4,400 feet and the average growing season is 125 days. Annual precipitation is 8-12 inches, most of which falls outside the growing season. Temperatures range from -30 to 104 degrees Fahrenheit with high winds being common, particularly in spring.