Common Starling - Behaviour

Behaviour

It is a highly gregarious species in autumn and winter. Flock size is highly variable, with huge flocks providing a spectacular sight and sound usually occurring near roosts. These huge flocks often attract birds of prey such as Merlins or Sparrowhawks. Flocks form a tight sphere-like formation in flight, frequently expanding and contracting and changing shape, seemingly without any sort of leader. Very large roosts, exceptionally up to 1.5 million birds, can form in city centres, woodlands, or reedbeds, causing problems with their droppings. These may accumulate up to 30 cm deep, killing trees by their chemical concentration; in smaller amounts, the droppings are, however, beneficial as a fertiliser, and therefore woodland managers may try to move roosts from one area of a wood to another to spread the benefit and avoid large toxic deposits.

Huge flocks of more than a million Starlings are observed just before sunset in spring in southwestern Jutland, Denmark. There they gather in March until northern Scandinavian birds leave for their breeding ranges by mid-April. Their flocking creates complex shapes against the sky, a phenomenon known locally as sort sol ("Black Sun"). To witness this spectacle, the best places are the seaward marshlands (marsken in Danish) of Tønder and Esbjerg municipalities between Tønder and Ribe.

Flocks of anything from five to fifty thousand Starlings form in areas of the UK just before sundown during mid winter. These flocks are commonly called a Starling "Moot".

Starlings are hunted by birds of prey, including the Peregrine Falcon and Brown Falcon. However, in the 1970s the consumption of chemically treated (DDT) crops by the starlings which were subsequently eaten by Peregrine Falcons caused a dangerous build-up of the toxin in the falcon. As a result, lower reproductive success was observed as a result of thinner eggshells and a build-up of organochlorine residues in eggs.

European Starling nests are especially vulnerable to predators such as stoats, foxes, and humans. Common Mynas are also a threat, as they often evict eggs, nestlings, and adult starlings from their nests.