The 2021 breeding season was the “least productive” on record for the Hen Harrier Project.

This year, 62 hen harrier breeding pairs were confirmed, with a further seven possible pairs also recorded. However, just 34 young birds were successfully fledged.

Of the 62 confirmed breeding pairs recorded in 2021, 18 pairs were successful in rearing and fledging young (30%).

The Hen Harrier Project monitors the numbers of territorial pairs of birds in designated special protection areas (SPAs) during the breeding season. Monitoring aims to establish the breeding outcome of each pair.

Worst year on record

The reduced number of young birds fledged this year follows a peak in 2019, when 81 fledged from nests across six SPAs. This was the highest number within the network in the last 15 years.

Of note from the particularly concerning performance in 2021, the 10 confirmed pairs in the Slieve Bloom Mountains fledged no young.

Evidence of ground predators habituating the conifer forests is the main reason for high rates of nest failure in the Slieve Blooms.

Elsewhere, three breeding pairs at the Mullaghanish to Musheramore Mountains SPA fledged six chicks, with the population continuing to stabilise following no breeding activity in 2014.

Seven pairs fledged four young at the Slieve Aughty Mountains, three pairs and two young were recorded at Slieve Beagh and five pairs fledged three young at the Slievefelim to Silvermines SPA.

The largest SPA, which includes the Stacks, Mullaghareirks, Mount Eagle and West Limerick Hills supports the largest population of breeding hen harriers in Ireland with 34 pairs recorded in 2021, a population which is 33% lower than it was in 2005. Nineteen young birds were fledged in the region this year.

Influences

The Hen Harrier Project said poor breeding productivity can be linked to habitat availability, habitat quality, predation pressure and weather.

“For the population to be capable of maintaining itself, or expanding, reproduction and survival must exceed the combined effects of mortality and dispersal to other areas.”

Describing the breeding rate, Minister of State for Land Use and Biodiversity Pippa Hackett said: “This goes to show just how difficult it is to turn the tide for this special bird, to deliver the right measures, to protect and enhance its habitat, and to keep it safe from predators.”

She said it was a “disappointing year” but encouraged all those involved in protecting and monitoring the native bird of prey to “keep up this invaluable work”.