Mobbing among birds is very common

Mobbing is an interesting piece of behaviour and it’s not confined to birds, writes Dick Warner

THE buzzard was having a bad day. It was trying to fly across the big field beside my house but it was being mobbed by 20 or 30 song birds of various species. The small birds were attacking it from above and behind, making loud alarm calls as they did so. As far as I could see all their dives were aborted at the last moment and no actual contact was made but it still must have been quite annoying for the buzzard.

Mobbing is an interesting piece of behaviour and it’s not confined to birds. As an example of convergent evolution it’s been observed among meerkats and sticklebacks, also California ground squirrels mob snakes and humpback whales mob killer whales. In fact Konrad Lorenz in his book On Aggression claimed that humans are subject to the same impulse to mob, although we are normally capable of bringing it under rational control.

There are obviously risks attached to getting close to a potential predator but the evolutionary rewards must make up for these to judge by how widespread mobbing is. Among birds it’s more common during the breeding season leading to the obvious conclusion that it’s designed to distract the predator and make it harder for it to spot vulnerable nests. As well as distracting the predator, the noisy mobbing also draws attention to it and alerts other birds over a wide area. Many small birds, including great tits, have a special mobbing call which is different to their usual alarm call and seems to be designed to rally troops to join the assault.

The buzzard I saw was being mobbed in October which is outside the breeding season of the birds attacking it. There is another theory that mobbing is used to educate juvenile birds so that they recognise threats. However, it’s interesting that buzzards mostly eat small mammals and don’t pose any great threat to songbirds and also that herons and cuckoos are regularly mobbed.

Occasionally, mobbing attacks can injure or kill the bird. This is particularly true when the mob consists of larger birds such as gulls or members of the crow family. I know of one instance where a young female peregrine was mobbed over several days by a flock of rooks and jackdaws and ended up so badly injured she was unable to fly.

There is another type of mobbing which is about getting food rather than protection from predators. Many gull species use this tactic, waiting until another bird, or an animal, has got hold of something edible then attacking in numbers to harass the misfortunate creature. A modified form of this behaviour is really what’s behind the stories of urban herring gulls attacking humans with food in their hands. Also many species of skua rely on mugging as their main source of food.