Tracking technology confirms controversial cause of Hen Harrier decline

Tracking technology confirms controversial cause of Hen Harrier decline

In the UK, Hen Harriers Circus cyaneus spend their summers on upland moors, nesting amongst the deep heather. They are one of our most treasured upland species, famous for their spectacular displays of sky-dancing and aerial exchanges of food during the breeding season.

Sadly, Hen Harriers are also one of our most persecuted birds of prey. The latest population survey estimates that just 575 pairs remain across the UK and the Isle of Man, despite there being enough natural habitat and food to support over 2,650 pairs.

An overwhelming body of scientific evidence now shows that the main reason for their population decline is illegal bird killing associated with the management of moorland for grouse shooting. Many areas of the UK’s upland moors are managed in this way, whereby landowners and gamekeepers maintain artificially high numbers of grouse which are then hunted during the shooting season (from 12th August onwards).

These landowners employ legal methods to control predators such as foxes, crows, weasels and stoats, but in some cases they also illegally kill predators such as Hen Harriers, Golden Eagles Aquila chrysaetos, Peregrine Falcons Falco peregrinus, Red Kites Milvus milvus (Near Threatened) and Northern Goshawks Accipiter gentilis.

The RSPB’s Hen Harrier LIFE project was set up to provide the conditions in which the Hen Harrier’s population and range could recover, particularly in areas where the species was most threatened, such as northern England and southern and eastern Scotland. We wanted to understand more about how the birds were living – and dying. So over the course of five and a half years, we fitted trackers to over 100 Hen Harriers.

We watched as each bird made its first flight away from its nest, with some birds making short trips within the UK and others making longer journeys to Ireland, France, Spain and Portugal. We watched as they made their own nests and raised broods of young chicks. But sadly, we also watched as they met their end.

“Sometimes, tags transmitting data with no signs of malfunction would suddenly and suspiciously stop, often over land managed for grouse shooting”

When a bird died naturally, the tag continued to transmit data and we could usually locate the remains, which were sent for an independent post mortem examination by a veterinarian. However, sometimes tags that were transmitting data regularly with no signs of malfunction would suddenly and suspiciously stop, often over areas of land managed for grouse shooting. These unexpected disappearances were reported to the police as they were indicative of illegal persecution.

We have incorporated what we’ve learned into the RSPB’s community engagement programme. So far, we have directly spoken to over 12,600 people, working with young gamekeepers, school children and other members of the community in key areas where Hen Harriers should be thriving, to raise awareness about these incredible birds and the sad ends many of them meet.

Now the project has ended, its legacy is a much better understanding of where and when Hen Harriers are dying, the scale of illegal killing and a much better-informed community. We are advocating for the sustainable and legal management of upland habitats, and the licencing of driven grouse shooting. With such a small population of Hen Harriers remaining, we are absolutely devastated whenever a bird is a victim of crime, and we strive to bring an end to all illegal killing of Britain’s birds of prey.

This article was first published by BirdLife International on 5 March 2020.

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