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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.

Taxonomy

The first formal description of Montagu's harrier was by the Swedish naturalist Carl Linnaeus in 1758, in the tenth edition of his Systema Naturae, under the binomial name Falco pygargus. The genus Circus was introduced by the French naturalist Bernard Germain de Lacépède in 1799. The genus name is derived from Ancient Greek. Circus is from kirkos, meaning "circle", referring to a bird of prey named for its circling flight (probably the hen harrier), and pygargus is Modern Latin derived from the Greek pugargos, from puge, meaning "rump", and argos, meaning "shining white". The species name was formerly used for the hen harrier before Montagu's was identified as a different species.

alt= Montagu's Harrier Male|thumb|Montagu's Harrier Male, Rollapadu Wildlife Sanctuary, Andhra Pradesh, India

Identification

thumb|Montagu's harrier (Circus pygargus) in flight from Tal Chappar

Plumage

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.

Flight

Montagu's harrier has a particularly graceful flight, 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.

thumb|Montagu's harrier (Circus pygargus) from Tal Chappar

Dimensions

Montagu's harrier is a deceptively small raptor, though it appears larger because of its large wing surface compared to small body weight, which gives it a typically buoyant flight. The female is larger than the male because the female needs to produce eggs, however this is not apparent in the field.

  • Wingspan:
  • Length: (tail: )
  • Weight (average):
  • Male:
  • Female:

Risk of confusion

Montagu's harrier can be confused with several species that exist within the same range. The most similar are the hen harrier and the pallid harrier. The male is easily distinguished from other species as its plumage is distinctly darker and more mottled than in the males of hen or pallid harriers. However, distinguishing females and juveniles is more difficult. Usually, Montagu's harrier appears more slender in flight than the hen harrier, with a longer tail, longer and narrower wings and more pointed "hands". Also its flight is more elegant than the hen harrier, with more elastic, almost tern-like wingbeats. The distinction between female pallid and Montagu's harriers is the most delicate and can only be made in good conditions as the proportions are similar. The best recognition character is the pale collar around the neck of female and juvenile pallid harriers which is not present in Montagu's.

Habitat

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 , 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.

thumb|Adult male

In short, Montagu's harrier requires a large open area for breeding, with sufficiently tall ground vegetation to afford cover without being overgrown. It favours posts on which both male and female can rest and survey the breeding area: these can be fenceposts, small trees, or rocky outcrops. When hunting, in any season, it prefers areas of low or sparse vegetation where prey is more visible. Densely settled areas are generally avoided and it is highly susceptible to disturbance.

Food and foraging methods

The diet consists mainly of small rodents, small birds, bird eggs, reptiles (including snakes) and large insects (mainly Orthoptera, which are numerically the most common).

The population for the western Palearctic is estimated at 35,000–50,000 pairs. The global population is unknown and could be anything between 150,000 and 200,000 individuals(Birdlife International, 2004). This uncertainty is due to the fact that most of the world's population is situated in Russia and former Soviet republics where it is not quantified.

The evolution has been paradoxical throughout the 20th century. In the beginning of the century up to the 1940s, during a period when other raptors greatly decreased because of human persecution, Montagu's harrier actually increased its population and breeding range, breeding for the first time in Denmark in the 1900s, and greatly increasing elsewhere. However, from the 1940s onwards it has decreased rapidly. This is due to several negative factors: first, the massive use of agricultural pesticides such as DDT and other environmental poisons was extremely detrimental to the harriers themselves, as well as rarefying their prey, in particular large insects. The modification of agricultural practises, with an evolution towards more intensive farming also puts pressure on harriers, with faster growing crops preventing those birds that nest in farmlands from finishing their nidification before their clutches are destroyed by harvesting machines. Despite a generally negative trend there are local cases when the population has increased, such as in Sweden or in Germany

Further reading

  • Clarke, Roger (1996), Montagu's Harrier (book)
  • Werkman, Elvira (2021), The Amazing Story of Montagu's Harrier - How birds show us the way to agriculture and nature in balance (book) ISBN 978-90-9034857-5
  • Montagu's harrier species text in The Atlas of Southern African Birds
  • Website of the Harrier Conservation International
  • Satellite tracking map - Migration and breeding ecology of Montagu's harriers (Spain)
  • Ageing and sexing (PDF; 5.9 MB) by Javier Blasco-Zumeta & Gerd-Michael Heinze