Later this year, there will be a full survey of breeding Hen Harriers in the UK. Today’s blog by Simon Wotton, Senior Conservation Scientist, explains the reason for this survey and how you can help.
The last national survey of this UK red-listed species of conservation concern was in 2016, when the population was estimated at 545 territorial pairs (95% confidence interval, 447–664), a 14% decline in the population between 2010 and 2016. The national survey in 2004 estimated a population of 749 (675-832) territorial pairs, a 27% decline between 2004 and 2016.
In 2016, Scotland remained the stronghold for UK Hen Harriers with an estimated 460 (359-573) territorial pairs, around 80% of the UK population, but 9% lower than the 2010 estimate of 505 (418-612) pairs. The west Highlands continued to provide a home for the majority of Scotland's breeding harriers (175 (100-256) territorial pairs), while Orkney and the Hebrides were the only areas of the country to show a slight increase in numbers between 2010 and 2016.
Hen Harrier male on heather (c) Andy Hay (rspb-images.com)
The 2016 survey also revealed that the Hen Harrier remained on the brink of extinction as a breeding species in England as the population fell from 12 pairs in 2010 to just four pairs in 2016. The Hen Harrier population had been slowly recovering in Wales since re-colonising in the late 1950s but the 2016 figures showed that the number of pairs had fallen by more than a third over the past six years, from 57 to 35 territorial pairs. This is the lowest population that has been seen in Wales for over a decade. Northern Ireland also experienced a decline between 2010 and 2016, from 59 to 46 territorial pairs.
Longer term figures highlight the decline in the UK hen harrier population between 2004 and 2016.
What will the next survey show?
The 2023 survey will provide updated estimates of population size and national and regional trends since 2016. As a high-profile species of great conservation concern, current information on status across the UK range is vital. The survey partners are RSPB, Natural England, NatureScot, Natural Resources Wales, Northern England Raptor Forum, the Northern Ireland Environment Agency, the Northern Ireland Raptor Study Group and the Scottish Raptor Study Group (SRSG).
The survey area (the species’ known range) has been defined using results of the last survey and more recent records through consultation within the RSPB, the statutory conservation agencies, Raptor Study Groups, and through records submitted to BirdTrack and eBird since 2016.
Hen Harrier female in flight (c) Mark Thomas (rspb-images.com)
In Scotland, non-random ‘census’ coverage of core areas will be carried out mainly by volunteers (mainly SRSG members), and randomly selected 10km squares will be surveyed in the rest of the range, mainly by RSPB field staff.
Elsewhere, it is expected that comprehensive coverage will be achieved of all suitable 10km squares within the Hen Harrier range in England, Wales and Northern Ireland. The other survey partners are Natural England, Northern England Raptor Forum, Natural Resources Wales and the Northern Ireland Raptor Study Group.
Field surveys will follow the well-established two to three visit method between late March and the end of July, giving the advantage of good comparability with previous surveys. If no birds have been seen, or breeding has not been confirmed, during the first two visits, a third visit may be made between late June and the end of July.
How you can help
If you think you have seen a Hen Harrier during the survey period, please report the sighting to henharriers@rspb.org.uk
Reports of sightings should include the date and location of sighting, with a six-figure grid reference or w3w where possible. A description of the bird’s behaviour would also be useful.
Male Hen Harriers are an ash-grey colour with black wing tips and a wingspan of just less than a metre. They are also known as ‘ghost birds’ because of the paleness of their plumage. Female Hen Harriers are slightly larger, are owl-like in appearance, and have a mottled brown plumage, which camouflages them when they nest on the ground. They have horizontal stripes on their tails, giving them the nickname ringtail and a patch of white just above, on the rump. You can see more here.
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