The Madison Valley IBA contains riparian cottonwoods and willows along the Madison River surrounded by shortgrass prairie. Ennis Lake is at the northern end of the IBA. The gallery forest supports 14 bird species of state conservation priority, and the lake is a major stopover site for migrating Common Loons and waterfowl. Almost all of the land within the IBA is privately owned, and the valley is experiencing a serious increase in housing developments that are converting open space into subdivisions.
Creation of the IBA was a cooperative partnership among the Madison Valley Ranchlands Group (a non-profit group of private citizens dedicated to protecting the ranching way of life, open space, and wildlife in the valley), the Rio Tinto-BirdLife International Partnership Action Fund, Luzenac America (a subsidiary of Rio Tinto that operates a talc mine in the valley), and Montana Audubon.
In 2003 and 2004, Montana Audubon biologists surveyed 11 tracts of riparian cottonwoods and willows along the Madison River and adjacent tributaries repeatedly throughout the breeding season. We also counted waterbirds at Ennis Lake during spring and fall migration periods and obtained information from Audubon volunteers on birds seen in the valley from 2000 to 2005. The site supports more than 160 species of birds, at least 70 of which breed in the riparian corridor. Fourteen of the riparian species are of conservation priority in the state; seven of these were common enough to have occurred on every survey unit (Red-naped Sapsucker, Downy Woodpecker, Willow Flycatcher, Least Flycatcher, Warbling Vireo, Gray Catbird, Song Sparrow). The site also supports four breeding pairs of Bald Eagles. Three pairs of Ferruginous Hawks nest in the valley and hunt within the IBA, and three pairs of Sprague?s Pipits nest on a patch of native prairie in the IBA.
Ennis Lake is a major stopover for migrating Common Loons in fall. It is not unusual to see more than 200 loons on a good day in late October. Peak counts have reached 300 birds, and the total number of loons that use the lake during fall migration is much higher than the number seen on any give day. The number of ducks using the lake in fall exceeds 20,000 each year, with the most abundant species being American Wigeons (5,000) and Redheads (>10,000). Numbers of American Coots routinely reach 15,000-20,000 during this same period. Ennis Lake is also a major stopover for spring waterfowl, especially Red-breasted Mergansers. In total, 24 species of ducks, two species of geese, and two species of swans have been recorded on Ennis Lake in recent years, and it is clear that the lake supports major concentrations of waterfowl.
Most of the Madison Valley is privately owned, and open space is decreasing as new housing developments occupy former ranchlands. The understory vegetation in the cottonwood gallery forest has been overgrazed by livestock and native ungulates in many places, and cowbird parasitism has become a problem for some species.
Of the lands in State ownership, 5.5% are school trust lands, 1.8% fishing access sites along the Madison River and Ennis Lake, and 22% consists of the lake proper. The bulk of the IBA consists of private lands used for cattle ranching and hay production.
The Madison River riparian zone is made up of cottonwoods (mostly black cottonwoods), willows, and water birch. The surrounding uplands are dominated by shortgrass prairie with scattered conifers (Douglas fir, limber pine, and junipers) and shrubs, including small patches of sagebrush.