The western marsh harrier (Circus aeruginosus) is a large harrier, a bird of prey from temperate and subtropical western Eurasia and adjacent Africa. It is also known as the Eurasian marsh harrier. Formerly, a number of relatives were included in C. aeruginosus, which was then known as "marsh harrier". The related taxa are now generally considered to be separate species: the eastern marsh harrier (C. spilonotus), the Papuan harrier (C. spilothorax) of eastern Asia and the Wallacea, the swamp harrier (C. approximans) of Australasia and the Madagascar marsh harrier (C. maillardi) of the western Indian Ocean islands.

The western marsh harrier is often divided into two subspecies, the widely migratory C. a. aeruginosus which is found across most of its range, and C. a. harterti which is resident all-year in north-west Africa.

Taxonomy

The western marsh harrier was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Falco aeruginosus. Linnaeus specified the locality as Europe but restricted this to Sweden in 1761. The western marsh harrier is now placed in the genus Circus that was introduced by the French naturalist Bernard Germain de Lacépède in 1799. The genus name Circus is derived from the Ancient Greek kirkos, referring to a bird of prey named for its circling flight (kirkos, "circle"), probably the hen harrier. The specific aeruginosus is Latin for "rusty".

Two subspecies are recognised:

Food and feeding

It hunts in typical harrier fashion, gliding low over flat open ground on its search for prey, with its wings held in a shallow V-shape and often with dangling legs.

It feeds on small mammals, small birds, insects, reptiles, and frogs.

It still faces a number of threats, including the shooting of birds migrating through the Mediterranean region. They are vulnerable to disturbance during the breeding season and also liable to lead shot poisoning. Still, the threats to this bird have been largely averted and it is today classified as Species of Least Concern by the IUCN.

Sources

Further reading

  • Marsh harrier at RSPB's Birds by Name
  • Birds of Britain - Marsh Harrier
  • Western Marsh Harrier or European Marsh Harrier species text in The Atlas of Southern African Birds
  • Western Marsh-Harrier text, map & photos at Oiseaux.net
  • Ageing and sexing (PDF; 5.7 MB) by Javier Blasco-Zumeta & Gerd-Michael Heinze