Montagu's harrier (Circus pygargus ) is a migratory bird of prey of the harrier family. Its common name commemorates the British naturalist George Montagu.
The Montagu's harrier is a migratory bird of prey. Adult males are characterized by their overall pale grey plumage contrasting with black wingtips. Adult females have mostly pale yellow-brown underparts, the belly with longitudinal stripes and spotted wing coverts. The upperparts are uniform dark brown except for the white upper tail coverts ("rump"), and the sightly paler central wing coverts. The juvenile birds resemble the females, but their belly and underwing coverts are not spotted, but uniformly red-brown in color.
Montagu's harriers breed in Europe, Asia, and Africa. Birds from Eurasia spend the winter in sub-Saharan Africa, while those from the eastern part of the range migrate to the Indian subcontinent. In Europe, they travel over a broad front, crossing the Mediterranean at various points, and only a small number are observed at migration choke points. Western birds don't go further south than the gulf of Guinea, but some eastern birds travel as far as South Africa. Montagu's harriers nest mostly in broad river valleys, plains, and levels bordering lakes and the sea. They can breed in wetlands and also utilize heaths, dunes, moors, and can be found in the steppe. They adapt to shrublands in gorse or heather and to areas planted with young conifers. When no other suitable habitat is available these birds will nest in agricultural farmlands. For breeding, Montagu's harriers require a large open area, with sufficiently tall ground vegetation.
Montagu's harriers can be both solitary and gregarious at times, both during the breeding season and in winter quarters. They are diurnal and hunt by day. As these birds have a wide distribution, they will take whatever prey is available in the area where they are. Prey is caught while flying along fixed routes at low heights and constant low speeds. Their flight is considered lighter and more dexterous than other harriers enabling them to take more agile prey. When possible Montagu's harriers often follow the edges of various vegetation to catch their prey by surprise. This is taken after a short stoop, though fast running animals and flying birds can be chased over a short distance. Montagu’s harriers are generally silent birds, but during the breeding season and near the nests, they become noisy.
Montagu's harriers are carnivores. They feed mainly on small rodents, small birds, bird eggs, reptiles (including snakes) and large insects.
Montagu's harriers are generally monogamous and form long-lasting pair bonds. However, males may be polygynous and will mate with two females. The breeding season begins with the return of both partners to the nesting site, at which point both the male and the female will start displaying. The display consists of various sky-dances and aerobatic figures that vary according to each individual. Both sexes will display, crying loudly, though the males' displays are more frequent and spectacular. A breeding pair may associate with others to form loose colonies, with as many as 30 nests in the same area, sometimes as close as 10 m (33 ft) apart. The nest is built by the female, always in tall vegetation. It is a simple construction made of grass, used only for one season. The female lays 3 to 5 eggs and incubates them for 27-40 days. The chicks leave the nest after 28-42 days and are independent 2 weeks later. Montagu's harriers breed for the first time when they are 2 or 3 years old, but occasionally one-year-old females may attempt to nest.
The main threats to Montagu's harriers include the massive use of agricultural pesticides such as DDT and other environmental poisons, as well as rarefying their prey, in particular large insects. The modification of agricultural practices, with an evolution towards more intensive farming, also puts pressure on Montagu's harriers; many nests are destroyed by harvesting machines because the harvesting of crop fields is done during the breeding season. In some countries, Montagu's harriers are still illegally killed during migration.
According to the IUCN Red List, the total Montagu’s harrier population size is around 100,000 to 499,999 mature individuals. The European population is estimated at 54,500-92,200 breeding females, which equates to 109,000-184,000 mature individuals. According to the European Raptors Biology and Conservation resource, specific populations of the species have been estimated in such areas: Russia: 20,000 - 35,000 pairs; Belarus: 3,000 - 5,000 pairs; France: 3,800 - 5,100; Spain: 2,500 - 10,000 pairs or 4,000 - 5,000 pairs according to another research. In Germany: 377 - 428 pairs and in Bavaria – 153 pairs. In total, a European population is around 35,000 - 65,000 pairs. Overall, currently, Montagu’s harriers are classified as Least Concern (LC) on the IUCN Red List but their numbers today are decreasing.