Hen Harrier numbers fall by one third, new study finds

Published by Ian Carey on

22nd April, 2016

Ireland’s hen harrier numbers have fallen by one third since 2000, a shocking new study has found.

Despite serious efforts to protect this incredible and rare species the population has continued to fall.

Several factors are to blame for the decline including the intensification of agriculture, dense forestry, and uncontrolled burning of uplands.

As top predators, the decline of Hen Harriers may be linked with declines in availability of their preferred habitat, changes in habitat quality and associated effects on food availability.

Hen Harriers are renowned for their spectacular aerial courtship displays known as the ‘skydance’.  Traditionally, Hen Harriers breed in open upland habitats, using heather, pre-thicket forest plantations or scrub for nesting while feeding on small birds and mammals.

The 2015 National Survey of Hen Harriers (the fourth national survey since 1998-2000) has shown that the national population has experienced further declines, including within some former strongholds for the species.

The current national population estimate of 108-157 breeding pairs in 2015 represents a decline of 8.7% since the 2010 national survey, which recorded 128-172 pairs.

These results indicate a decline of 16.4% in the national Hen Harrier population since 2010.  A comparison of the survey area which was covered in all four national surveys (since 1998) indicates that the population has fallen from 110-155 pairs during the first national survey in 1998–2000, compared with 95-130 pairs in 2015, which is an overall decline of approximately one third (-33.5%) over this 15 year period.

The fourth national survey of Hen Harriers in 2015 was undertaken by a partnership of the Golden Eagle Trust, Irish Raptor Study Group and BirdWatch Ireland on behalf of the National Parks and Wildlife Service.

Dr. Allan Mee, survey coordinator with the Irish Raptor Study Group, commented on the specific pressures faced by harrier populations.  “There was a wide range of different pressures recorded in the national survey, both within and outside SPAs, and many of these warrant further investigation.  Pressures such as forest maturation, clear-felling, wind energy production, agricultural intensification, uncontrolled burning and degradation of important open habitats such as heather moorland, turf cutting, and recreational disturbance were all recorded by observers during the study.  It is important to understand why some harrier populations may be declining, and a comprehensive and scientifically robust action plan is needed to maintain or enhance existing Hen Harrier populations into the future.

The results of the 2015 national survey will serve to inform the Hen Harrier Threat Response Plan which is currently being prepared by the National Parks and Wildlife Service with input from a wide range of relevant stakeholders.  The purpose of this plan is to identify the main threats to Hen Harriers and identify integrated solutions and actions required for a sustainable management of the species.  If the plan is successful, it has the potential to deliver an effective framework for conservation of the Hen Harrier and other priority upland birds and habitats.

Ireland is required under European law to designate Special Protection Areas (SPAs) for the protection of endangered species of wild birds.

In 2015, harrier populations in several of the SPA areas were found to have declined, with an overall decline of 26.6% since 2005.  Speaking of these trends, John Lusby, survey coordinator with BirdWatch Ireland, commented: “The fact that the SPA network holds 44% of known pairs in the country, which is a significant proportion of the population, shows just how important these areas are in the national context.  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.

Dr. Marc Ruddock, survey coordinator with Golden Eagle Trust, commented on the efforts involved: “This is one of the largest surveys of its kind, and would not have been possible without the significant investment of so many skilled surveyors, which is nothing short of phenomenal.  That so many devoted their time and energy to the survey is hugely positive and demonstrates the passion that is out there to help understand and help conserve Hen Harrier populations in Ireland.  To all those involved we extend our considerable thanks and appreciation.

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Ian Carey

Ian is the editor of the Green News. He works as Communications Manger with the Irish Environmental Network.