Hen Harrier

The Hen Harrier Programme Report

The Hen Harrier Programme monitors the number of breeding hen harrier, a protected Irish raptor, in each of the Special Protection Areas (SPAs) designated for this species. During the 2020 breeding season, 58 confirmed and four possible breeding hen harrier territories were identified within these SPAs. The population estimates within SPAs for 2020 is therefore 62 pairs. This estimate is lower than that of recent years (70 pairs in 2017 and 68 in 2018), but similar to that of last year (63 pairs). However, the overall SPA hen harrier population is down 32% compared to 2005.

Of the 62 pairs assumed breeding in 2020, there were a total of 60 fledged young recorded in six SPAs designated for this species. The Mullaghanish to Musheramore SPA had five confirmed pairs, which fledged ten young. The Slieve Aughty Mountains SPA had six confirmed pairs, which fledged six young. The Slieve Beagh SPA had two confirmed pairs, which fledged five young. The Slieve Bloom Mountains SPA had ten confirmed pairs, which fledged three young. The Slievefelim to Silvermines SPA had five confirmed pairs, which fledged three young. Finally, the Stack’s to Mullaghareirk Mountains SPA had 30 confirmed pairs, which fledged 33 young.

Along with declines in the national population of hen harrier, there have been substantial declines in the number of breeding pairs in our largest SPAs since the mid-2000s. The largest SPA, the Stack’s to Mullagherierk Mountains SPA, has undergone a serious decline since it was designated in 2005, with a decline of 33% in the number of breeding pairs. However, the population of this SPA has stabilised in recent years. Furthermore, the second largest SPA, the Slieve Aughty Mountains SPA, has undergone a 74% decline in breeding pairs of hen harrier since designation in 2005. However, the long-term trend for the remaining SPAs is considered to be stable.

The number of fledglings per pair is a good measure of breeding success. There are a number of factors that influence the success of a nest, including, habitat quality, predation, weather and disturbance. Research indicates that the number of chicks per pair must exceed 1.45 for the hen harrier population to remain stable. The SPA monitoring data, from 2015-2020, show that the mean fledgeling rates range from 0.99 to 1.25 chicks per pair. The number of fledged young per pair for the 2020 breeding season was 1.02. These numbers are below that required for the SPA populations of protected hen harrier to be self-sustaining.


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