The Blue Tit is a small, brightly colored passerine. It measures about 11–12 cm in length and weighs between 9 and 12 grams. Its plumage features a blue head with a white stripe across the face, a greenish back, and bright blue wings and tail. It feeds mainly on insects and spiders in the spring and summer, while in the winter it supplements its diet with seeds and berries. The Blue Tit is resident throughout most of its range but may undertake short altitudinal migrations. It prefers deciduous and mixed forests, as well as gardens and urban parks. It nests in natural or artificial cavities, laying between 7 and 13 eggs that are incubated for about two weeks.