Montagu's harrier (Circus pygargus) is a species of harrier, a bird of prey in the family Accipitridae. It breeds in large open areas in the Palearctic and is migratory, wintering in Africa, the Indian subcontinent and parts of the Arabian Peninsula. Its common name commemorates the British naturalist George Montagu.
Sexual dimorphism is particularly apparent in the plumage of this species. Adult males are characterized by their overall pale grey plumage contrasting with black wingtips. Compared with other harriers this species has characteristic black bands along the secondaries, both above and below the wing and rusty streaks on belly and flanks. Adult females have a broadly similar plumage to that of pallid and hen harriers. The underparts are mostly pale yellow-brown, the belly with longitudinal stripes and the wing coverts spotted. The upper parts are uniform dark brown except for the white upper tail coverts ("rump"), and the sightly paler central wing coverts.
The juvenile plumage resembles that of the female, but differs by the belly and under wing coverts which are not spotted, but uniformly red brown in colour.
A melanistic form occurs regularly in this species. In this form the male is much darker than usual, with a black head, brownish black above and grey underparts. The melanistic female is entirely chocolate brown except for grey flight feathers. Partially melanistic morphs can also be found.
Montagu's harrier has a particularly smooth flight pattern, with powerful and elegant wingbeats which give an impression of buoyancy and ease. In true harrier fashion it searches the countryside, flying low, and generally holds its wings with a marked positive dihedral.
This species can be found in a middle-latitude band of predominantly temperate climates, but also in Mediterranean, and boreal zones. Although it has been found nesting up to 1,500 m (4,900 ft), it is essentially a lowland species, and nests mostly in broad river valleys, plains, and levels bordering lakes and the sea. It can breed in wetlands, though these are often smaller and drier than those used by the marsh harrier. It also utilizes heaths, dunes, moors, and can be found in the steppe. It adapts to shrublands in gorse or heather and to areas planted with young conifers.
When no other suitable habitat is available this harrier will nest in agricultural farmlands where it is vulnerable to early harvesting. Amongst these it chooses especially grasslands and cereal crops such as wheat, barley, oats and colza. In western Europe, up to 70% of the population breeds in artificial habitats.
