Gulls are utterly fearless, as shown by this remarkable image of a white-tailed eagle under attack.
Herring gulls dive-bomb predatory birds at a steep angle from above and behind, as they make a piercing shriek - "kaiow!".
The attacks typically occur when the gulls are defending themselves and are most frequently seen during the breeding season, when adults protect vulnerable offspring. Some gulls also defecate or even vomit on the predator for good measure.
So-called "mobbing" usually starts with one or two gulls, but may eventually attract a large number. "They nest in large, densely packed, noisy colonies and often gang up on a predator," says Pat Monaghan, a professor of animal ecology at the University of Glasgow in the UK.
"They use mobbing to great effect," she says. Even Monaghan has come under attack during the course of her studies. "They kick you in the head - their claws are sharp and can cut."
"It's often suggested that using birds of prey, flown by falconers, might act as a gull deterrent," she says. "This picture suggests otherwise."
Despite their aggressive, quarrelsome and omnivorous nature, Europe has seen a significant decline in herring gulls, lesser gulls and great black-backed gulls, the three largest populations. For example, figures from the UK's Joint Nature Conservation Committee suggest the British breeding population of herring gulls has halved since the late 1970s.
The cause of the declines is not yet known but could be the result of changes in their maritime environment, including pollution or developments in commercial fishing practices, says Monaghan.
"Because the number breeding in urban areas has increased (though still a small percentage of the overall UK population), people do not realise that the herring gull is disappearing from our coasts," she says. "They might sadly fall silent one day."
Image: Markus Varesvuo/naturepl.com. This post originally appeared on New Scientist.