The starling (Sturnus vulgaris) is a medium-sized passerine bird in the family Sturnidae. This common and widespread species is also known as the common starling, or simply the starling in the British Isles. It breeds in open habitats throughout Europe, Asia and North Africa. It has adapted to live in urban areas and is now a largely resident breeder across its range. Some populations are migratory and move southwards after breeding; this pattern appears to be increasing as winters become milder further north. The nest is usually built in a natural cavity or old nest site of another animal such as a woodpecker; if these are not available it will happily use an artificial site such as a hole drilled into brickwork or even an upturned dustbin lid!
This highly gregarious species often forms huge flocks outside the breeding season typically consisting of several thousand birds. Starlings have stout bodies with short necks and legs, black upperparts glossed with green or purple, pale gray underparts and yellow eyes. They have strong feet which they use to perch on trees and buildings; consequently they often roost communally on prominent sites such as TV aerials where predators cannot reach them easily. Starlings can mimic the calls of other birds including those of hawks, making them difficult to protect smaller garden birds from predation by these mimics.
During winter many starlings congregate at traditional roosting sites which can hold up to one million birds! These spectacular displays often attract attention from both humans and predators alike so finding safe roosting sites is vital for the survival of these flocks during this time. One such predator is the peregrine falcon which has been known to take advantage of these large gatherings by preying on them en masse; however studies have shown that while individualstarlings may be at risk from predation at these communal roosts, overall predation rates are actually lower than would be expected given the density of prey present.
It seems then that there is some form of predator avoidance behaviour going on here whereby individualstarlings benefit from being part of a larger group but how exactly this works remains something of a mystery!