New study into the diet of reintroduced white-tailed eagles shows they’ve been eating about 70 different types of food – but not lambs.
Juvenile white-tailed eagles pose no threat to livestock, a study from Forestry England has found.
The birds on the Isle of Wight have been found to enjoy tucking into a varied diet of hares, rabbits, fish, cuttlefish and even a marine invertebrate. While there had previously been fears that the eagles would feed on livestock, such as lambs, the project has found no evidence of this.
Typically, diet studies on white-tailed eagles involve analysing the prey remains in a nest at the end of the breeding season. But this hasn’t been an option for this project, as all the birds haven’t been old enough to breed – with the exception of one pair last year who bred unexpectedly young.
“We’ve had to really innovate with our diet study, spending thousands of hours in the field watching these birds,” says Steve Edgerton-Read, the White-tailed Eagle Project Officer at Forestry England. “The advantage of watching the birds in the field is that, not only do we know what they’re eating, but we understand how they’re acquiring those meals as well, building an incredibly detailed picture of how these birds are living in the landscape.”
The study revealed that as the eagles aged, both the prey items and their feeding strategies changed. Younger birds fed more on mammals and relied more on carrion. As they matured, they fed more on fish and cuttlefish, and became more adept at hunting live prey – and at piracy.
“This is when white-tailed eagles effectively steal meals from other predatory birds, such as grey herons, marsh harriers, buzzards and red kites,” adds Edgerton-Read. “That’s a really important ecological role that had been lost within the landscape and is being restored.”
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In 2019, six white-tailed eagles were reintroduced on the Isle of Wight by Forestry England and the Roy Dennis Wildlife Foundation. Further reintroductions have taken place since and in total, 29 birds have been reintroduced. Of these 29, 15 have survived to date, within the expected mortality rates for this species, with losses due to a mix of natural and human causes. This population was boosted by a chick last year – the first time the species has bred in England in 240 years.
Main image: © AinsleyBennett