The hen harrier is one of the UK’s rarest birds of prey. Once widespread across the UK, habitat loss and illegal persecution have caused hen harrier numbers to plummet, making them a red-listed species of high conservation concern. But just how rare are hen harriers in the UK today? Let’s take a look at the population trends and conservation status of this iconic bird of prey.
Hen Harrier Population Trends
Hen harriers have experienced severe population declines since the 19th century. The widespread drainage of wetlands and agricultural intensification lead to the loss of their preferred nesting and foraging habitats. Persecution by gamekeepers on grouse moors also took a heavy toll on hen harrier numbers.
By the late 1800s, hen harriers were extinct in many parts of their former range. In the 20th century, populations continued to decline dramatically. Between 1900 and 1970, hen harriers were reduced to just one or two pairs in England and Wales. Scotland fared slightly better, but still experienced substantial losses.
Efforts to protect hen harriers began in the 1950s, but recovery was slow. By 2008, there were an estimated 630 pairs across the UK. While this was an improvement on earlier decades, it represented less than 10% of historic hen harrier numbers.
Since 2008, hen harrier populations have fluctuated with no clear upward or downward trend. The most recent national survey in 2016 estimated there were 460 pairs in the UK. The fluctuations reflect ongoing conservation efforts and pressures facing hen harriers. Illegal persecution remains a major limiting factor on populations, despite increased legal protection.
Geographic Distribution
Hen harriers now occupy a fraction of their former breeding range in the UK. They are found mainly in upland areas of northern and western Britain, in particular:
- Orkney Islands
- Northern Scotland
- Southern Uplands of Scotland
- Northern England Pennines
- Wales
The strongholds are Orkney, where around 20% of the UK population occurs, and mainland Scotland which holds 60% of pairs. England and Wales combined account for just 20% of the total population. Within their current range, hen harriers nest in concentrated pockets wherever suitable habitat exists. The overall range is highly fragmented rather than continuous.
Rarity Status
Hen harriers are classified as Near Threatened on the global IUCN Red List. At a country level, they are red-listed as a UK conservation priority species. There are estimated to be less than 700 breeding pairs in the UK. Hen harriers are also listed on Schedule 1 of The Wildlife and Countryside Act 1981, affording them additional legal protection from disturbance or harm.
Several criteria qualify hen harriers as red-listed and near threatened:
- Population size – Small and declining overall population
- Range size – Restricted to less than 10% of former UK range
- Population concentration – Over 50% located in 10 or fewer sites/locations
Due to these factors, hen harriers are considered endangered and at high risk of extinction in the UK without continued conservation management. Their rarity status highlights the need for habitat protection and restoration to support the remaining fragile populations.
Causes of Decline
What are the main reasons behind the hen harrier’s alarming population crash and its continued rarity across the UK? Several man-made factors have shaped the decline of these birds over the past two centuries.
Habitat Loss
The drainage of wetlands for agriculture removed vast areas of natural hen harrier habitat. An estimated 90% of UK lowland heath and bog areas were lost between 1800 and 1980. As their preferred nesting, roosting and foraging grounds disappeared, hen harrier numbers dwindled. Remaining habitat became fragmented and isolated. Intensive agriculture also reduced prey availability in farmland around their upland habitat strongholds.
Illegal Persecution
Hen harriers are killed illegally because some gamekeepers see them as a threat to red grouse stocks on moorland managed for shooting. Despite being protected by law, hen harriers are still routinely shot or trapped on grouse moors. Persecution is the leading cause of death for many hen harriers fitted with tracking tags. Illegal killing hampers hen harrier recovery, particularly in areas of suitable habitat like the English Pennines.
Forestry
In the early-mid 20th century, large areas of open moorland were afforested, removing potential nesting sites for hen harriers. The enclosed, shaded environment of conifer plantations is unsuitable. Clear-felling timber crops can temporarily create new opportunities, but forests tend to discourage hen harriers in the long-term.
Climate Change
Hen harriers rely on moist, boggy areas with tussocks of heather or tall grass for nesting cover. Hotter, drier summers associated with climate change degrade this habitat. Heather beetle outbreaks linked to rising temperatures may also reduce nesting cover over the long-term in some areas.
Disturbance
Outdoor recreation activities like hiking near nest sites, habitat management operations and construction of wind farms may disturb hen harriers, leading them to abandon nesting attempts. As populations decline, they become more vulnerable to localised disturbance effects.
Conservation Actions
To protect hen harriers and aid the recovery of populations in the UK, conservation organisations and governments carry out a range of actions:
Habitat Protection
Designating Special Protection Areas (SPAs), Sites of Special Scientific Interest (SSSIs) and Nature Reserves safeguards remaining fragile habitats. For example, over 30 designated sites protect core areas for hen harriers in Scotland. Restricting damaging activities helps preserve habitat quality.
Habitat Restoration
Managing land for breeding birds involves practices like controlled burning of heather to create favoured nesting structure and conditions while ensuring sufficient cover remains. Drain blocking and bog restoration re-wets degraded areas, providing hunting grounds.
Protection on Grouse Moors
In areas intensively managed for grouse shooting, measures like diverting footpaths away from nests and suspending spring burning near nests aim to prevent disturbance and illegal persecution of hen harriers. Some moorland managers are trialling ‘brood management’ schemes, though these are controversial.
Monitoring and Tracking
Conservation groups and governments carry out national surveys of breeding hen harrier populations every 5-6 years to monitor trends. Satellite tagging of individual birds provides detailed data on movements, survival rates and causes of death. However, many tagged birds still disappear illegally.
Law Enforcement
Illegal persecution remains difficult to monitor and tackle, especially in remote areas. But increased use of technology like tagging helps build evidence on causes of death. Prosecuting those responsible raises awareness of the consequences and acts as a deterrent. However, more enforcement is frequently called for.
Working with Landowners
Partnership projects involving government agencies, NGOs and landowners aim to promote hen harrier-friendly practices. For example, the Heads Up for Hen Harriers initiative works with grouse moor owners to improve attitudes and reduce persecution. Such co-operation is vital for success.
Outlook and Challenges
What does the future hold for hen harriers in the UK, and what are the remaining challenges for ensuring their recovery?
Future Population Trends
Populations are predicted to remain relatively stable at between 400-600 pairs in the near future based on current trends. However, numbers could decline if illegal killing worsens or funded conservation action decreases. Alternatively, recovery may occur through habitat management and reduced persecution but is unlikely to be rapid without major change across grouse moors.
Recolonising England
The re-establishment of hen harriers as a regular breeding species in England is a major challenge. Persecution on potential habitat in the Pennines and other upland areas has kept numbers there close to zero. Significant habitat restoration and protection would be required to allow English populations to recover.
Climate Change Impacts
Hotter, drier summers and increased frequency of droughts and wildfires may degrade hen harrier habitat in the long-term. But modelling suggests parts of Scotland could remain relatively suitable by the 2080s if persecution is stopped. The north of Scotland should remain a stronghold.
Grouse Moor Conflict
Tension between hen harrier conservation and grouse shooting interests continues to undermine efforts to allow populations to recover on moorland. A licensing scheme for grouse moors was proposed but is now delayed. Without resolving this conflict, illegal killing will likely persist.
Funding Pressures
Conserving rare species like hen harriers requires long-term, labour intensive and costly interventions. But budgets for monitoring and habitat management work are often short-term and prone to cuts. Maintaining funding levels needed to sustain conservation work remains a challenge.
Case Studies
To illustrate hen harrier conservation in practice, here are two case studies from different parts of the UK:
Orkney Hen Harrier Project
Funded by Scottish Natural Heritage and RSPB Scotland, this 10-year project focused on conserving hen harriers on Orkney, where the largest UK population exists. Achievements included:
- Annual monitoring of breeding success at over 100 nest sites.
- Tagging young hen harriers to study mortality and dispersal.
- Providing nest protection on farmland through liaison with land managers.
- Managing habitat through techniques like rotational heather burning.
Outcome: The Orkney population grew from 80 to around 120 pairs over the project’s duration from 2006 to 2015, representing 20% of UK total.
Lake Vyrnwy Hen Harrier Project
Lake Vyrnwy in Powys, Wales is an RSPB Nature Reserve identified as having high potential for nesting hen harriers. The RSPB carried out habitat and predator management from 2015 to attract harriers. This involved:
- Controlling predator numbers of foxes, crows and raptors.
- Burning heather patches to create diverse nesting structure.
- Providing perches for hunting and nesting materials.
- Employing summer staff to monitor activity.
Outcome: In 2018 hen harriers bred at Lake Vyrnwy for the first time in over 20 years, with 4 chicks successfully fledged. Monitoring and management continues annually.
Summary and Conclusion
In summary, the hen harrier has declined from a relatively widespread species to one of the UK’s rarest birds of prey. The population now stands at fewer than 700 breeding pairs, largely confined to Scotland and Orkney.
Habitat loss, illegal killing, afforestation and climate change have all contributed to their demise. Ongoing conservation work aims to stabilise numbers through habitat protection and restoration, law enforcement, population monitoring and liaison with landowners.
Key challenges remain around tackling persecution on grouse moors, maintaining funding for conservation actions and bolstering the English population. While populations may fluctuate at current low levels short-term, a substantial recovery seems unlikely without major breakthroughs in hen harrier-friendly land management. Their conservation will require collaboration, compromise and commitment from all stakeholders going forwards.
