All three plumages have a conspicuous white rump patch. An extensive study of the behaviour and breeding biology of this species in the Amherst area was carried out by Acadia University graduate student Robert Simmons in 1980-83. He found up to 20 nests each year in the area with, as usual in this species, some strongly territorial males mated to more than one female. Range Breeds north to northern Alaska, northwestern Mackenzie, northern Manitoba, central Quebec and probably Newfoundland, south to middle and southwestern United States. Winters from British Columbia, southern Ontario and Nova Scotia to Colombia and the West Indies.
Additional races occur in Europe and Asia.
Although the food of this hawk consists largely of mice and other small rodents, it eats a variety of other animals. While canoeing on the Cornwallis River above Kentville in August 1942, I twice flushed Northern Harriers from among marginal reeds, so close it was apparent they had been disturbed while feeding. Investigation revealed a small salmon, long dead, half-devoured, and a freshly killed frog that had been neatly and adeptly skinned. On 2 September 1949 I saw one at Canard, Kings County, sitting on the ground with its wings slightly extended, obviously holding its prey. When approached, the hawk carried its victim a short distance, but finding it too burdensome soon dropped it.