| Northern Harrier (Circus hudsonius) (Linnaeus, 1766) |
| Synonyms: Circus cyaneus hudsonius |
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Circus hudsonius breeds throughout the northern North America from Alaska to Newfoundland, including the northern United States; patchily in the western and central states. Mainly migratory and winters in USA, Central America, and the Caribbean. C. hudsonius nests in marshes, meadows, wet prairies, old fields, and pastures; up to 2,400 m; in various open habitats in winter. Arrives on the breeding grounds in March-April, and depart in August-November. Closely related to Hen Harrier (C. cyaneus); likely conspecific. Medium-sized raptor, with long wings, tail, and legs (41-52 cm in length; 97-120 cm wingspan; weight 300-750 g); sexually dimorphic. Adult male is dark grey above, and mainly white below, with black wing-tips; adult female is brown above, and whitish or tan below, streaked with brown. Yellow iris and white rump in both sexes. Monogamous or polygynous. This species nests in dense, tall vegetation (often in cattails); the nest is a platform built of cattails, grasses, and sedges, and raised above water level or the ground. Clutch size 4-6 eggs; incubation, by female only, 31-32 days. Male delivers food during incubation and early in the brooding (10-14 days). The young can walk within a few days and may move into the adjacent vegetation, if disturbed. They are on the wing at 5-6 weeks. Adults are often vocal and aggressive near nest, and may dive at and strike intruders. Northern Harrier hunts on the wing while flying low over the ground, mainly for small mammals (especially voles, Microtus spp.), but also birds, frogs, and insects.
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