National Elk Refuge and Yellowstone National Park is through Grand Teton National Park, so while easily seen anytime of the year, they are most numerous in the spring and fall. Other ungulates in the park include moose, bison, and pronghorn—the fastest land mammal in the western hemisphere. The park's moose tend to stay near waterways and wetlands. Between 100 and 125 bighorn sheep dwell in the alpine and rocky zones of the peaks. Over 300 species of birds have been sighted in the park including the calliope hummingbird, the smallest bird species in mainland North America, as well as trumpeter swans, which is North America's largest waterfowl. In addition to trumpeter swans, another 30 species of waterfowl have been recorded including blue-winged teal, common merganser, American wigeon and the colorful but reclusive harlequin duck which is occasionally spotted in Cascade Canyon. Both bald and golden eagles and other birds of prey such as the osprey, red-tailed hawk, American kestrel and occasional sightings of peregrine falcon have been reported. Of the 14 species of owls reported, the most common is the great horned owl, though the boreal owl and great grey owl are also seen occasionally. A dozen species of woodpeckers have been reported, as have a similar number of species of warblers, plovers and gulls. The vocal and gregarious black-billed magpie frequents campgrounds while Steller's jay and Clark's nutcracker are found in the backcountry. The sage covered plains of Jackson Hole are favored areas for sage grouse, Brewer's sparrow and sage thrashers, while the wetlands are frequented by great blue heron, American white pelican, sandhill crane and on rare occasions its endangered relative, the whooping crane. The Snake River fine-spotted cutthroat trout (or Snake River cutthroat trout) is the only native trout species in Grand Teton National Park. It is also the only subspecies of cutthroat trout that is exclusively native to large streams and rivers. Various researchers have not been able to identify any genetic differences between the Snake River fine-spotted cutthroat trout and the Yellowstone cutthroat trout, though in terms of appearances, the Snake River subspecies has much smaller spots that cover a greater portion of the body, and the two subspecies inhabit different ecological niches. The Snake River fine-spotted cutthroat trout was identified by some researchers as a separate subspecies by the mid-1990s, and is managed as a distinct subspecies by the state of Wyoming, but is