Sea eagles are Britain’s biggest birds of prey, with wings shaped like barn doors spanning over over eight feet. They were persecuted to extinction in the early 19th century, but are now being reintroduced under a government programme begun in the 1970s.
Their return, however, has not been welcomed by crofters in north west Scotland. They have previously blamed the birds for taking more than 200 young lambs and damaging their livelihoods.
But the new study, conducted for the Scottish government’s wildlife agency, Scottish Natural Heritage, suggests that these claims were exaggerated. Less than two per cent of deaths amongst lambs could be attributed to sea eagles, it concluded.
Researchers examined lamb mortality on the Gairloch peninsula between April and August last year. At one croft only two out of 100 lambs were lost, and at another only two out of 160 were known to have died.
Post mortem examinations of six dead lambs from these and other crofts found evidence that death had been caused by an eagle in just one case. One carcass had puncture wounds in its head and neck “consistent with being inflicted by long powerful talons”.
Other carcasses showed signs that they had been eaten by eagles, but this was probably after they had died from other causes. Eagles are known to scavenge on the bodies of lambs that have died on the hill during birth.
The study, carried out by the UK government’s Food and Environment Research Agency, also found that lambs only made up between four and 14% of the diet of sea eagles. They prefer to eat seabirds like fulmars, and fish, which they swallow whole.
There are only about 40 breeding pairs of sea eagles, also known as white-tailed eagles, in Scotland. The birds, which sometimes can been seen in Mull, Skye and elsewhere on the west coast, are still being illegally poisoned by a few farmers or gamekeepers.
The Scottish environment minister, Roseanna Cunningham, described the reintroduction of sea eagles as “an outstanding success”. But she accepted that crofters were “rightly concerned”.
She said: “Where there are problems with sea eagles predating on livestock, we will look at maintaining and improving schemes to find ways to help farmers manage their stock to coexist with these magnificent birds.”
Dr Alison MacLennan, the Skye and Lochalsh conservation officer for the Royal Society for the Protection of Birds, expressed sympathy “with the distress caused to farmers and crofters through the loss of their livestock, for whatever reasons.”
But the evidence indicated that eagles tended to take lambs that were still born rather than to kill them, she argued. This was reinforced by the finding that their diet included blackface lambs, which gave birth on the open hill, but not cheviots, which gave birth under supervision close to farms.
Ewen Mackinnon from Scottish Crofting Federation, pointed out that lamb mortality last year was less than in previous years. “This is good news for the year 2009 but also leaves open to question what might be the yearly variations in predation impact,” he said.
He called for “continued vigilance” in the future. “We all share the objective of minimising lamb losses to ensure the economic sustainability of sheep management in the area,” he added.