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18 Dec 2020

Welcoming back the ghost of the moor

Written by Shaila Rao, Ecologist
A hen harrier in flight. It has a predominantly white body, with black-tipped wings.
The ghost of the moor – a male hen harrier and Sorrel’s father (© Hamish Smith)
Despite continued persecution limiting their numbers across the UK, the spectacular hen harrier made a dramatic return to breed on Mar Lodge Estate in 2016.

It’s a chilly May morning in the Cairngorms as I scrabble up through the heather to reach an isolated, statuesque granny pine tree on the hill. I take my usual seat, protected from the cold northerly wind by the gnarled trunk of the tree, pick up my binoculars and start to scan. Patience and vigilance are the name of the game here. An hour passes and I can feel the biting wind creep into the crevasses in my clothes and a drip form on the cold tip of my nose. But then, as if from nowhere, it happens. Into my field of view the ‘ghost of the moor’ appears. He’s a long way off but a male hen harrier is making his way up the glen, floating over the heather ridges and bumps like a fulmar riding the sea waves. My eyes start to water as I keep firmly fixed on the male as he comes closer and approaches the nest site. In a flash, the female appears with her distinctive white rump – obviously keen for food to feed the fast-growing chicks. She calls expectantly and harries the male at speed. He responds, dropping the prey into a regularly used patch of grass among the heather. She swoops down, spends a few moments plucking the prey, then takes to the air and follows her usual flight line back into the nest. Five minutes and it’s all over!

To observe hen harriers in the field, particularly a food pass, is a truly memorable and special experience, and one that many more people should have the opportunity to see. However, these birds of prey are few and far between in Scotland. In the early 1800s hen harriers were common and widespread throughout the UK, but by 1900 they had been almost driven to extinction. This was in part due to reduced breeding habitats as a result of agricultural intensification, but more significantly from human persecution to protect poultry and game. Hen harrier populations recovered a little in the 1940s when many gamekeepers were away serving in the Second World War and young conifer plantations providing suitable nesting habitats were established by the Forestry Commission. However, persecution of this species, primarily attributed to driven red grouse shooting practices, has continued and is the main factor limiting the recovery of hen harriers in the UK. This has resulted in the Scottish Government proposing a new licensing scheme for grouse shooting, which should hopefully be beneficial to the health of hen harrier populations.

It’s against this gloomy backdrop that something remarkable happened at Mar Lodge Estate. In 2016 a pair of hen harriers bred on the estate for the first time in living memory and went on to successfully rear four chicks. This pair returned in 2017 and produced a further two chicks. Incredibly, and probably linked to a peak in vole numbers, seven pairs of harriers nested in 2018, followed by seven again in 2019 and five in 2020. In the boom breeding year of 2018, a total of 24 hen harrier chicks fledged from Mar Lodge Estate. To put this into perspective, it compares with no successful breeding attempts in Deeside in the same year and only nine in the whole of England, producing 34 chicks.

It’s notoriously difficult to find the nests of hen harriers and this breeding information has come on the back of many, many hours of searching, patient observation and carefully timed visits to nests (under licence). We can only speculate why hen harriers have returned to Mar Lodge in such a dramatic fashion. We had often been told that Mar Lodge is too high up and cold for hen harriers – this is clearly not correct, with nests now recorded here up to 572m in altitude. Their return is most likely related to a number of factors. The first is the abundant availability of suitable nesting habitats, which have developed due to the reduction in grazing pressure here. Secondly, the lush ground vegetation and expanding woodland habitat may support an abundant prey base of species such as voles and meadow pipits for the birds. Finally, hen harriers are a sociable species, often nesting relatively close to one another and frequently interacting. It may be that the presence of harriers on the ground draws in other birds as they fly over the estate. What has been particularly interesting about the re-colonisation at Mar Lodge, for a species renowned as a moorland inhabitant, is that many nests have been located close to the forest edge or even within areas of young pines and the harriers frequently hunt in the open woodland.

Fledgling hen harriers flying low over moorland.
Recently fledged young hen harriers among Scots pine regeneration (© Richard Orren)

Satellite tags have been increasingly used for hen harriers to learn more about their ecology and movements, but also to improve our understanding of their fate. We’ve been lucky to host a couple of successful nesting hen harriers that were satellite-tagged elsewhere in Scotland. One of these birds in particular has a great story to tell – ‘Sorrel the traveller’.

A person is holding a hen harrier bird, showing it's back, which has a satellite tag attached.
Sorrel as a chick when first satellite-tagged (© Hamish Smith)

Sorrel fledged and was satellite-tagged in 2016 from Langholm Moor in the Scottish Borders by the Hawk and Owl Trust as part of a Natural England hen harrier project. She spent the first year and a half of her life in southern Scotland, before making the long journey up to Mar Lodge Estate in spring 2018. Thanks to a heads-up from the Hawk and Owl Trust, we picked her up here and went on to watch her hook up with a male and raise three chicks successfully. Sorrel departed Mar Lodge in August 2018 and returned to Langholm Moor. But this is when her amazing travels really began. Between September 2018 and April 2019, Sorrel returned to the Grampian mountains (September), flew down to the Isle of Man (October) and then across to Ireland for the winter (October–March 2019).

A map of of Scotland and Northern Ireland, showing the flying pattern of a particular hen harrier.
Map of Sorrel’s movements from July 2016 to August 2018 (route follows letters in alphabetical order) (© Hamish Smith)

In spring 2019 our hopes were raised when Sorrel made two brief visits to Mar Lodge Estate, flying back and forth from Arran on both occasions, as well as making a foray north to the Dornoch Firth. But Sorrel chose not to breed here (perhaps no available males were present) and she spent the rest of the spring and summer of 2019 in Arran and overwintered in Ayrshire.

A map of of Scotland and Northern Ireland, showing the flying pattern of a particular hen harrier.
Map of Sorrel’s movements from August 2018 to April 2019 (© Hamish Smith)

So what about this year? Well, in spring 2020 Sorrel left her wintering grounds and once again returned to Mar Lodge flying via Arran. We were really excited to hear from the Hawk and Owl Trust that she was back with us and it was such a thrill to see her again. She arrived in early May – late in the day, as all of our other pairs of hen harriers were already incubating eggs. But we had observed a ‘spare’ male kicking around this year and in record speed Sorrel had got together with him, mated and started nesting. We watched Sorrel and her mate closely over the breeding period and once again she successfully raised three chicks. Sorrel is a satellite-tagging success story. She is now four years old, has successfully bred twice with us at Mar Lodge and she has opened our eyes to the long-distance travel that these birds undertake.

A map of of Scotland and Northern Ireland, showing the flying pattern of a particular hen harrier.
Map of Sorrel’s movements from April 2019 to August 2020 (© Hamish Smith)

However, it’s not all good news. The success of hen harrier breeding at Mar Lodge Estate led to us being involved in the RSPB Hen Harrier Life Project and through this 14 harrier chicks from Mar Lodge Estate were satellite-tagged between 2016 and 2020. But of these 14 chicks, only one still survives in 2020 – a female named Tamara, who spends much of her time in Perthshire. Eight of the satellite tags stopped suddenly, with no trace of a bird or body found, raising suspicions of possible foul play.

A female hen harrier chick, with speckled downy feathers.
Tamara, the satellite-tagged female hen harrier chick still surviving from Mar Lodge Estate

It’s been a pleasure to welcome back the ghost of the moor to Mar lodge Estate and we hope that breeding numbers here will go from strength to strength. We also hope that the issues with hen harrier persecution can be addressed and the success we have experienced can extend the breeding range of this magnificent bird across Scotland.

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