The habitat surrounding Blackfoot Reservoir is a mix of dryland grain fields and native sagebrush steppe with aspen pockets and basalt outcrops. The reservoir has several islands, covered mostly with native sagebrush habitat, but also with some willow riparian. Gull Island is used by nesting American White Pelicans, Double-crested Cormorants, California Gulls, and herons. The reservoir is storage for irrigation water, thus can experience low water by late summer. The reservoir is also important as a fishery for stocked rainbow trout and native Yellowstone cutthroat trout.
Gull Island, a 2.5 hectare island in Blackfoot Reservoir, supports the largest nesting colony (1400 nests) of American White Pelicans in Idaho. This island also supports one of the largest nesting colonies of Double-crested Cormorants (300+ nests) and California Gulls (6,000+ nests) in the state. An active Great Blue Heron, Black-crowned Night-heron, and Snowy Egret rookery can be found here as well. The reservoir itself is also used by waterfowl, waterbirds, and shorebirds during the summer, and possibly migration.
This reservoir can be drastically lowered for irrigation needs. This is especially a problem in drought or low water years. This impacts the fishery and possibly reduces the bird's food base. Low water can also leave the nesting island exposed to increased disturbance or predation. Fisheries managers are concerned about pelican and cormorant impacts on stocked rainbow trout, and on native Yellowstone cutthroat trout (a species of special concern in the state). Sportsmen are also concerned about bird impacts on recreational fishing in the reservoir. To address this issue, fisheries biologists conducted a two-year study on pelican and cormorant food habits on the reservoir. They found that these birds do have a significant impact on stocked fish, and have adjusted fish stocking timing to alleviate this problem. To reduce impact of pelicans on Yellowstone cutthroat trout, various methods of bird deterrence have been implemented during the sensitive trout migration period.
Blackfoot Reservoir is an open water reservoir with several islands. The islands are primarily sagebrush type habitat with some willow riparian. The surrounding uplands are primarily sagebrush habitat with pockets of lava outcrops and patches of aspen.
Blackfoot Reservoir is used as water storage for irrigation needs. However, it is also used extensively by the recreating public for fishing.