The resurgence on Orkney of the Hen Harrier, a red-listed species of high conservation concern, follows a period of steep decline on the islands, particularly between 1980 and the late 1990s. The breeding population has reached a 20-year high of 100 breeding females producing over 100 chicks.

A study to determine the cause of decline, funded by RSPB Scotland, Scottish Natural Heritage and University of Aberdeen, has revealed a direct link between the number of sheep grazed on land favoured by hunting Hen Harriers and the success of the species. Food shortage was determined to be the primary cause of the fall in numbers, especially at the start of the breeding season when the males hunt for both themselves and the females in order to bring them into good breeding condition.

It was found that the number of sheep grazing on moorland fringes in the rough grasslands that constitute Hen Harrier hunting grounds doubled during the period of decline, resulting in habitat degradation and a shortage of prey. With a shift in agricultural support payments the number of grazing sheep was reduced by 20% between 1998 and 2008, and the fortunes of the Hen Harrier improved significantly as the areas they preferred to hunt in were allowed to regenerate.

The Orkney Hen Harrier scheme started in 2003 and was one of the first new voluntary initiatives proposed as part of SNH's Natural Care programme.

The Hen Harrier - Circus cyaneus - is a bird of prey that breeds throughout the northern  hemisphere. It migrates to more southerly areas in winter.

Description

The male is mainly grey above and white below except for the upper breast, which is grey like the upperparts, and the white rump. The wings are grey with black wingtips. The female is brown above with white upper tail coverts.  Juveniles are similar to females with underparts buff streaked with brown.

Call

The male calls chek-chek-chek, or chuk-uk-uk-uk during his display flight. The female gives a whistled piih-eh when receiving food from the male and her alarm call is chit-it-it-it-it-et-it.

Food

Hen Harriers hunt small mammals and birds.

Breeding

They breed on moorland, bogs and farmland. The nest is placed on the ground. Four to six whitish eggs are laid.

Conservation Status –Least concern

This species has a large range, with an estimated global extent 1–20 million km², and a population estimated at 1.3 million individuals. There is evidence of a population decline, but the species is not believed to approach the thresholds for the population decline criterion of the ICUN Red List.

In the UK, the Hen Harrier suffers illegal persecution by gamekeepers and their employers on shooting estates, particularly those managed for Red Grouse shooting, resulting in local and regional extinction in many areas, particularly in England where only 4 breeding pairs survive despite abundant suitable habitat capable of holding several hundred pairs. Because of this they are now very rare in many parts of the UK, and under threat in many more areas.