Hen harrier numbers in Ireland are continuing to decline, according to the results of a new survey.
The number of breeding pairs has also declined even within special areas of conservation set up to protect the bird.
The fall in numbers was caused by a number of factors, including land use change, decline in habitat and reduced food availability, according to the 2015 survey, which was produced by the Golden Eagle Trust, Irish Raptor Study Group and BirdWatch Ireland, on behalf of the National Parks and Wildlife Service.
The 2015 survey showed there are between 108 and 157 breeding pairs across Ireland, down by 8.7 per cent since the 2010 survey, the research team said.
The numbers were determined by 250 field workers, who spent about 7,000 hours collectively surveying the bird of prey.
The survey would not have been possible without the work of these field workers, said survey coordinator Dr Marc Ruddock, of Golden Eagle Trust.
The hen harrier is best known for its “skydance”, a spectacular aerial courtship display, BirdWatch said.
They breed in upland habitats, nesting in heather, thickets or scrub.
Described as a “valuable indicator of the health of Ireland’s countryside”, the fall in numbers indicates the raptor remains under pressure, despite being a top predator.
The situation may be worse than the numbers indicate, given the decline of breeding pairs in “special protected areas” (SPAs) set up to promote the breed.
SPAs were set up in 2007 under the EU Birds Directive in upland areas of Co Clare, Co Cork, Co Galway, Co Kerry, Co Laois, Co Limerick, Co Monaghan, Co Offaly and Co Tipperary.
In 2015, harrier populations in several SPAs were found to have declined, with an overall decline of 26.6 per cent since 2005, the researchers found.
These SPAs, representing 2.3 per cent of Ireland's land area, are important, given that they hold 44 per cent of all known harrier pairs in the country, said John Lusby, survey coordinator with BirdWatch Ireland.
“The current survey results confirm that populations within parts of the SPA network are declining, and without intervention through appropriate management further declines at certain sites are anticipated,” he said.
Data from the survey will inform attempts to halt the decline through the Hen Harrier Threat Response Plan, currently being prepared by the National Parks and Wildlife Service.