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.