The Rough-legged Hawk is a circumboreal species that in North America, breeds north of timberline in Canada and Alaska including most of Newfoundland, the islands of the Canadian Arctic, as well as the Aleutians Islands. In western Canada, breeding has not been proven south of 60 degrees of latitude except at Churchill, Manitoba. The most southerly breeding takes place in central Newfoundland. The altitudinal limits on the breeding grounds appear to be about 3,000 feet (930 meters).
The winter range is well south of the breeding range and the coniferous forest belt that stretches across Canada. Most wintering takes place between southern Canada and the first two tiers of states south of the 49th parallel, but birds have been recorded as far south as New Mexico and Texas, especially during incursion years. The southeastern United States and southern Texas are devoid of winter birds. The northern limit of the breeding range occasionally extends up the west coast to Alaska and includes every Canadian province. The greatest number of birds wintering in the United States occur west of the Mississippi River. There are probably at least a few sight records for every state in the counterminous United States with wanderers to Bermuda and Mexico on occasion.
There are few places that could logically harbor Rough-legged Hawks on a year-round basis due to the wide separation between the summer and winter ranges. Zones of overlap are not known but there are older references to year -round occurrence on Southampton Island, north of Hudson Bay. Alaska is the only state that might claim continuous year-round presence of this species but the summer and winter ranges there do not overlap. This is also the case for Manitoba, Ontario, Quebec, and Newfoundland that have both summering and wintering birds within their geographical boundaries.
Three subspecies are recognized in the world but only one occurs in North America, namely Buteo lagopus sancti-johannis. This is the breeding race for all of Canada. Its range includes the Yukon and Northwest Territories including Prince Patrick, Melville, Bathurst, Banks, Baffin, and Somerset and Ellesmere islands, although breeding has not been proven at this latter location. Breeding also occurs around the perimeter of Hudson Bay and across Northern Quebec to central Newfoundland. It apparently does not occur in Alaska which is considered a zone of hybridization between North American and Eurasian type birds. Wintering occurs within North America.
MIGRATION
Movements south to the wintering range can occur early in years of low food supply. Some birds have been seen on the wintering range as early as August but departure from the breeding range is commonly during September and stragglers may still be there during October. Abundant food supplies will detain birds longer at northern latitudes. Arrival in southern British Columbia, at 50 degrees latitude, can be as early as late September with most of the movement during the latter part of October. The same appears to be true for the Great Lakes region as well. Some eastern hawk observers report southbound movements still occurring ahead of cold fronts in January, indicating that movement around the wintering range may occur as birds adjust to changing conditions.
Spring migration movements at the southern limits of the wintering range can begin in February. March and April are months of increasing movement with most birds passing the western Canada-United States border during April with late birds still moving until about the third week of May. Movements in the Great Lakes area can be quite strong from early March and continue well into May. Migration across the northern boreal forest belt and around Hudson Bay, can still be underway during June when some local birds are already sitting on eggs.
Birds cross the boreal forest zone in their quest to find suitable wintering habitat and again upon their return to the breeding grounds. Corridors are not well known, but concentrations have been noted at some hawk lookouts such as 1,000 on October 18, 1959 at Marathon, Ontario near the north shore of Lake Erie. Perhaps the proximity of a large water body served to concentrate the birds. Birds of southern Baffin Island and northern Quebec probably travel down the east side of Hudson Bay and thence southwesterly towards Lake Superior. Following a more southerly route across the lake brings the birds in a positive direction towards the areas of greater winter concentration on the Great Plains. Other movements out of the central Arctic probably take place in a more direct north-south fashion as birds move into the mid-west prairies. Birds banded in Alaska have been recovered in Colorado indicating that at least some travel in southeasterly direction to reach the mid-west. Interior migration through British Columbia in the fall is not heavy, suggesting that most Alaskan birds bound for United States wintering grounds pass east of the cordilleran ranges.
Spring movements are strong in the Great Lakes area but they are not all directed in a northeasterly line. Possibly birds moving up the eastern Great Lakes are bound for different breeding grounds than those moving through the western Great Lakes area. Here, they can display a north or northwesterly trend as they cross Lake Superior. Spring counts along the south shore of Lake Ontario produce 400 to 600 birds per season at Derby Hill. Combined totals of up to 2,000 birds from all lookouts have been noted during the spring season as birds move through the Great Lakes region. Western concentrations have not been noted in the same numbers and coverage of the northern central plains in a systematic way by hawk watchers is limited so that comparative numbers are not available.
Historical information and more recent systematic counts at hawk- watching stations show larger number of migrants moving in some years than in other years. Spring migration counts do not always correspond with counts taken the previous fall and "flight" years do not necessarily correspond with southerly invasions of other more northerly species such as Snowy Owls or Goshawks. Correlations with known population fluctuations have not been demonstrated.
#Which species has this range?;question\Q12\Q12.wav
