Hen harrier

The hen harrier (Circus cyaneus) is so named because it was formerly believed to prey on domestic fowls, which is one reason why it was subject to persecution. In more recent times it has been unjustly blamed for being a threat to grouse populations, with the result that the hen harrier has been a protected species in the UK for a number of years. However, it is still a “red list” bird that is very much under threat.

The species breeds in many temperate and cold zones in Europe, Asia and North America, in the last of which it is known as the northern harrier.

When food becomes scarce in the upland regions hen harriers tend to migrate south for the winter, often being seen, from around October to April, in the New Forest near the south coast of England. The open areas of the Forest are a lowland version of their breeding grounds, but with more food on offer at this time of the year.

Appearance

The female hen harrier can be up 55 centimetres (21 inches) long with a wingspan up to 118 centimetres (46 inches). Male birds are slightly smaller. Adult males and females have a similar shape but very different plumage. Male birds are mostly blue-grey but with black wingtips, whereas the females are brown with a white rump and barred tail, which accounts for the name “ring-tail” by which they are sometimes known. The markings around the face give the female a somewhat owl-like appearance.

Behaviour

Hen harriers hunt (for small birds and mammals) by over-flying a piece of ground in a systematic way, sometimes flapping their wings and sometimes gliding with the wings held in a shallow V shape. They will study an area with great intensity, sometimes checking it several times before moving on.

During the winter, hen harriers congregate in communal roosting areas on the ground. They can sometimes be seen gathering in the sky before swooping down to the ground for the night.

Breeding

The UK breeding range of the hen harrier is the upland moors of Scotland, Wales and Northern England, which coincides with the regions maintained as grouse moors, hence the clash with the gamekeeping fraternity. The male bird has an elaborate courtship flight involving dives, swoops, somersaults and rolls. Both birds build their nest, in April or May, on open ground and consisting of twigs and grass. The clutch is usually three to five eggs, but can be larger.

Incubation, which is done solely by the female, is up to 30 days, during which time the male brings food to her. When the chicks hatch the male continues to do all the hunting, giving food to the female which she then divides among the nestlings. Fledging begins at around 35-40 days.

© John Welford