Hen harriers have undergone large changes in
distribution and abundance in the UK and are red-listed because of
population declines during the period 1800–1995 (Eaton et
al 2009). The species was virtually eliminated from mainland
Britain during the 19th century, almost certainly due to
persecution by gamekeepers, although land use changes may also have
played a part. During this time, populations of hen harriers
persisted on Orkney and the Western Isles of Scotland. They
returned to mainland Britain during the 20th century, probably
initially due to reduced gamekeeping activities during the two
world wars. By the mid–1970s the British population was estimated
at 500 pairs, with a further 250–300 pairs in Ireland (Watson
1977).
A national survey in 1988–89 estimated that
the UK and Isle of Man had 478-669 pairs (Bibby & Etheridge
1993). About one third (33%) of the pairs nesting in Scotland
(excluding Orkney) were recorded in young forestry plantations,
with the remainder on grouse moor (27%) and other heather moor
(38%). It was thought that the distribution of harriers would
change as forestry plantations matured and the habitat became less
suitable for nesting and foraging hen harriers. These predictions
were borne out by the results of the 1998 national survey (Sim
et al 2001) when the estimate of 570 territorial pairs
suggested no significant change from that of the 1988-89 survey. In
Scotland (excluding Orkney), 55% of hen harriers were found to be
nesting on grouse moor, 29% on other heather moor, and only 11% in
young plantations.
The most recent national survey of hen
harriers, carried out in 2004, showed a 41% increase in the UK and
Isle of Man population to 806 territorial pairs (Sim et al
2007). In Scotland, the Orkney breeding population of hen harrier,
which had formerly acted as an important refuge for the species,
had increased from a decline which began in the late 1970s (Amar
et al 2003) and had reached a low point in the late 1990s
when the previous survey took place. Compared with the 1998 survey
however, in 2004 there were decreases in the East Highlands and the
Southern Uplands. Overall there were decreased numbers of harriers
breeding on grouse moor and signs of occupation of new habitats
with nearly 10% of the Scottish population associated with
brash/scrub and mature conifer plantation – two land management
classes from which there were no breeding records in previous
surveys (Sim et al 2007).
The UK has classified a suite of Special
Protection Areas (SPAs) for hen harriers. Incentives for
managing these sites for the benefit of hen harriers and other
qualifying species are available from government. SPAs and
other sites of national importance (SSSIs) for hen harriers are
monitored by the country conservation agencies. Together with
surveillance programmes covering the species and its habitats in
the wider countryside, this enables government to report to the EU
on the fulfilment of its obligations under the Birds Directive “to
ensure their survival and reproduction in their area of
distribution”. Such national reporting enables the EU to
assess the status of the species at European scale. In this
report we will refer to favourable conservation and favourable
condition targets, with Section 7 providing the context for
this.
Several studies have investigated the factors
influencing the distribution, abundance and productivity of hen
harrier. These studies have implicated a number of factors
including principally: habitat change (Redpath et al 1998,
Arroyo et al 2006, Amar et al 2008); persecution
(Etheridge et al 1997; Summers et al 2003,
Whitfield et al 2008b, Anderson et al 2009,
Redpath et al 2010) and prey abundance (Redpath &
Thirgood 1997, Amar et al 2003).
The conflict between hen harrier conservation
and grouse moor management has been highlighted by a number of key
publications, with the UK Raptor Working Group (Anon 2000)
providing a definitive overview on management and legal matters.
Recently, some important reviews have quantified the magnitude of
hen harrier persecution. For example, Redpath et al.
(2010) found that there were records of only 5 successful hen
harrier nests on the estimated 3,696 km2 of driven
grouse moors in the UK in 2008; an area of habitat estimated to
have the potential to support about 500 pairs.
There are some important on-going
activities to address the conflict. The Langholm Moor
Demonstration Project in south Scotland is exploring whether
economically viable driven grouse shooting and hen harriers can
co-exist. The Project, run by SNH, Buccleuch Estates, Game
and Wildlife Conservation Trust (GWCT), Royal Society for the
Protection of Birds (RSPB) and Natural England, is trialling
diversionary feeding of hen harriers (to divert them from grouse in
the breeding season). It is putting in place significant
improvements in land management practices (including muirburn,
predator control and livestock reductions), and has a well defined
programme of scientific monitoring (Langholm Moor Demonstration
Project 2011). This Project was borne out of discussions within
Scotland’s Moorland Forum, which is addressing wider issues
concerning the sustainable management of the uplands in Scotland
(Scotland’s Moorland Forum 2011). Natural England in
conjunction with the Environment Council is leading a conflict
resolution process to tackle persecution of hen harriers in England
(but with a reach to Scotland). The Environment Council, an
independent body with experience in conflict resolution, is
mediating discussions between interested parties in this conflict,
and many supporting papers have been produced as part of this
(Environment Council 2011). Some scientific studies have been
published recently on the conflict, with Redpath et al.
(2010) providing an overview of the current evidence base and
options for addressing the conflict.
This framework presented here complements and
extends earlier analyses of national hen harrier datasets by
looking for environmental factors that correlate with or are
otherwise associated with the distribution of breeding hen harriers
in the UK, and at a regional scale within Scotland. A
national survey of hen harriers was undertaken in 2010, and is
likely to report towards the end of 2011 or early 2012; a further
revision to the framework will be made on publication of that
survey.