Gulls dive-bomb predatory birds at a steep angle from above and behind, as they make a piercing shriek. Attacks typically occur when the gulls are defending themselves. Europe has seen a significant decline in herring gulls, lesser gulls and great black-backed gulls. The cause of the declines is not yet known but could be the result of changes in their maritime environment, says Pat Monaghan, a professor of animal ecology at the University of Glasgow in the UK.”]
Source: https://gizmodo.com/see-gull-take-on-eagle-in-mid-air-piggyback-attack-5856819