A harrier's face feathers are arranged into a disk. This helps the raptor to listen out for prey as the feathers form a groove, which direct sound waves to the ear opening.

Statistics
Hen harriers have a body length of 43-52cm, a wingspan of 99-121cm and weigh 0.3-0.53kg.

Physical description
Males are pale grey with black wing-tips and a white rump. Females and immature birds are brown and have a barred tail, and also have a white rump. They have a long tail and wings.

Distribution
Hen harriers range across North America, Europe and Asia.

Habitat
They inhabit moors, coastal marshes and reed-beds.

Diet
Hen harriers feed on small mammals and birds, and occasionally reptiles, amphibians and insects. When hunting, they fly low over the ground searching for prey. Once spotted, they swoop down for the kill. They are notorious for taking wounded gamebirds.

Behaviour
They migrate south of their breeding grounds in the winter. Outside of the breeding season, hen harriers sometimes gather in roosts of 10-20 individuals. Gatherings of up to 200 hen harriers have occasionally been recorded.

Reproduction
Egg-laying occurs in mid April to early July. The female incubates an average of 4-6 eggs in a nest made of reeds and vegetation on the ground. The male brings her food and feeds the chicks when they hatch after 30 days. The chicks fledge after 29-38 days, but are fed by their parents for a further few weeks. Males often breed with and support more than one female.

Conservation status
Hen harriers are not considered to be globally threatened, although their numbers do seem to be reducing. They are protected in England and urgent action is needed to save them from extinction here. Illegal persecution on moorland managed for grouse shooting is thought to be the main factor limiting the hen harrier breeding population in England.

Voice
Hen harriers emit a ke-ke-ke call when they are alarmed.