Golden eagle numbers in Scotland have risen to their highest level since comprehensive monitoring began, with more than 500 pairs recorded in a country-wide survey carried out in 2015.
And though the increase on the last census in 2003 of 15 per cent, from 442 to 508 pairs, means that the species can now be assessed as having “favourable conservation status”, numbers are still substantially below Scotland’s carrying capacity.
“For the survey, our team visited 729 ranges where there is evidence of golden eagles in the past,” said the RSPB Scotland’s head of species and land management Duncan Orr-Ewing. “We believe that Scotland could hold about 800 pairs in total.”
Orr-Ewing identified two distinct reasons why Britain’s top avian predator has failed to rebound completely from historically low numbers in the 19th century, despite complete protection afforded by UK-wide legislation.
“The North and West Highlands have been heavily over-grazed by deer and sheep over many generations,” he said, “so you have an impoverished landscape with low numbers of prey available. Eagles are present but they have low [breeding] productivity.”
Golden eagles are dependent on mountain hares and red grouse, but they will take a wide range of prey items including foxes and young deer, as well as feeding on carrion.
In the east of Scotland, from Cairngorms National Park to Moray, Grampian and Angus, there is a different problem: this is an area dominated by managing land for driven grouse shooting, and – consequently – there is plenty of prey.
“You would expect golden eagles to be thriving here,” Orr-Ewing said, “but out of 91 home ranges surveyed, only 34 are occupied.”
He said satellite-tagging of individual eagles and work by the RSPB’s investigations team has conclusively shown that illegal persecution is causing birds to disappear, and this is the reason why numbers remain low in this part of Scotland.
Nevertheless, this is the first time there has been a significant increase in the golden eagle population for nearly 35 years. The first three national surveys in 1982, 1992 and 2003 produced numbers of 424, 422 and 442 respectively.
Elsewhere, numbers in southern Scotland – Dumfries & Galloway and the Borders – continue to be low, with just three or four pairs, when the landscape has the potential for up to 16.
This has a knock-on effect on the recovery of the species in England, Orr-Ewing said – the last English golden eagle disappeared from Haweswater in the Lake District earlier this year, and the species is now regarded as extinct south of the border. “Unless something is done about eagle numbers in the south of Scotland, you won’t have them back in England,” he said.
Orr-Ewing pointed to habitat restoration work in both the north-west of Scotland and at Haweswater – the replanting of native trees such as birch and rowan, for example – that would, in time, improve prey numbers for golden eagles.
In the meantime, he concluded: “It’s good news that we have got this population increase, but we would describe this as a population recovery.”
Main image: There are more than 500 pairs of golden eagles in Scotland today. © Pete Cairns/RSPB Images