Mull eagle diary part 3: the threats to the eagles

Even our biggest bird of prey has enemies. RSPB warden Dave Sexton outlines the threats – both natural and man-made – to the white-tailed eagles of Mull

Main image by Ian McCarthy/RSPB Images

28th February 2017
Young eagles are vulnerable when they disperse from their natal territories

White-tailed eagles are the UK’s largest bird of prey – one of the largest eagles in the world – and you’d think they were virtually unassailable. However even our biggest avian predator has a few challenges to contend with – both natural and man-made.

Here on Mull, probably their biggest natural risk of injury or death is a clash with another eagle; either another sea eagle or a highly territorial golden eagle. Golden eagles have grudgingly accepted their long lost neighbours back into their former haunts but they still won’t miss an opportunity to aggressively escort one out of their airspace.

Golden eagles are by far the dominant eagle species of the two and nervy sea eagles usually take rapid evasive action when a manic goldie steams into view. We have had dead eagles of both species with tell-tale talon puncture wounds so fights do happen but like all big predators, they prefer to avoid conflict if they can, knowing what the outcome of a battle could be.

We’ve no foxes on Mull but elsewhere in Scotland a young eaglet newly out of the nest and on the ground could be vulnerable to a night-time attack if it fails to reach a safe perch to roost.

Agile and inquisitive pine martens can access eagle eyries and be a potential threat to eggs and chicks. They probably scent prey remains on the nest and climb up for a look; others have been known to make their dens in the base of these vast nest structures. Quite handy to have a food take-away just upstairs! Equally both fox and pine marten can end up as eagle prey so it works both ways.

Occasionally, we’ve had eagle casualties after they’ve flown into structures such as power lines or turbines but by far their most serious threat from mankind still (shockingly in 21st-century Scotland) comes from illegal persecution.

While great strides have been made to ensure sea eagles are publicly regarded, quite rightly, as a native British bird there is no doubt that for some land managers their presence remains a challenge. We work hard, with hill sheep farmers in particular who may face problems with eagles, to understand their concerns and seek workable, practical and pragmatic solutions.

It’s never easy but progress is happening. Sadly on some shooting estates there is zero tolerance to anything remotely predatory. One of our young Mull sea eagles left the safety of this island and ventured east and straight into trouble. I’d watched him over winter on Mull learning to hunt and how to steal fish off otters.

Young white-tailed eagle
Dave's young eagle

By the spring he was dead. He ate a poisoned mountain hare bait on a driven grouse estate placed on the hill to kill whatever ate it. For a hungry young sea eagle on his first big foray away from home, it was just too tempting. Nearby, every fence post had a cube of poisoned venison to pick off any buzzards that might spot an easy meal. It was a complete black-hole for predators. No one was ever prosecuted.

dead eagle
The young eagle, dead from poisoning

Back on Mull, thankfully, no such danger exists. That’s not to say there aren’t wildlife management conflicts to resolve but the presence of sea eagles is now seen as a normal part of daily island life (not to mention highly valuable for wildlife tourism). Whilst some bad old habits across Scotland have yet to end, the sea eagle population is growing steadily and their future, for now, seems bright.

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