Marsh harrier

The marsh harrier (Circus aeruginosus) is the largest of the three species of harrier that can be seen in the United Kingdom (the others are the hen harrier and Montagu’s harrier). As its name suggests, it frequents marshes, reedbeds and nearby fields, gliding at low level as it hunts for food.

The marsh harrier is resident in the warmer parts of Europe, but those in the north and east leave in August or September for Africa and the Middle East. In the United Kingdom it is only resident in a small region of the Thames Estuary, but is a summer visitor to East Anglia, the West Country and the area around Morecambe Bay in northwest England.

The marsh harrier is a regular visitor to wetland nature reserves in the areas mentioned above and so its future is not of immediate concern. However, its history of decline in numbers and subsequent recovery means that it has been given amber list status.

Appearance

The marsh harrier is about 50 to 55 centimetres (19-22 inches) in length, with the females being larger than the males. The wing span is 115-125 centimetres (45-49 inches). The tails and legs are long, and the wings are broader than those of other harrier species.

Male marsh harriers are generally dark brown on the back and coverts (front wing feathers), with the head being a lighter brown and streaky. The underside is a streaky reddish-brown. The central and hind parts of the wings and the tail are grey. The wing-tips are black.

Female marsh harriers are mainly chocolate brown with creamy-coloured feathers on the head, a dark eye-band and a lighter patch on the chest. The wings are much darker than those of the male birds although the hindwings are darker than the forewings.

Behaviour and feeding

In flight, the marsh harrier will flap its wings heavily several times then glide with the wings held in a shallow V-shape. At times it will soar higher. During courtship displays the male marsh harrier will dive with half-closed wings then shoot up, loop the loop and fall down again in a spin. When passed food by the male in mid-air, the female will fly on her back with claws outstretched.

Despite being an agile and rapid flyer, the marsh harrier takes all its food, comprising mainly small mammals and birds, nestlings, eggs and carrion, on the ground or from the water. Sometimes fish and frogs form part of the diet. Surprisingly, the marsh harrier has no interest in molesting ducks, which therefore show no fear of them.

The marsh harrier will perch on low posts and bushes. When walking it does so heavily.

Breeding

Marsh harriers return to their breeding grounds from late March to mid-April, with nest building taking place in May or June, The nest, of twigs and water plants, is built among the reeds.

The clutch comprises three to six eggs which are incubated by the female alone while the male brings food for her to the nest. Incubation takes anything from 30 to 37 days. The female only joins in hunting when the chicks are older. The latter will leave the nest before they are ready to fly, which they can do from 40 to 50 days after hatching. Only one brood is raised.

© John Welford