It is the largest bird among tomtits – 14 cm. The head is black with white
cheeks and neck. The back side is greenish, sometimes bluish. The stomach is brightly yellow with a black longitudinal strip. Males and young birds have broader strips.
It lives in forests and parks. More often than other tomtits it is settled near people. It seeks insects and spiders on branches and trunks of trees. In winter it eats seeds and other vegetable food. It is a usual visitor of feeding racks in city parks. Sometimes by December they can even take food from a stretched palm.
It prefers to build its nest at places with not of a thick deciduous forests, woods, parks, old fruit gardens and bushes along river banks. It is met in settlements with wood vegetation. At the period of building a nest it avoids places with pure coniferous forests. It builds its nest in hollows of tree trunks, in bays of constructions, in old nests of squirrels and birds of prey, and in other closed places. It uses thin branches, dry grass stems, moss, small roots, and lichen as a basis for its nests. It adds then down, wool, feathers, cocoons and web of spiders and insects, etc. It fills this mass the whole nest. In the heap of this construction material it makes a shoot and covers it with wool and horse’s hair sometimes with a mixture of vegetable down and feathers. The sizes of nests are differs greatly depending on a chosen space for a nest, but the sizes of the shoot are more or less the same: 40 – 60 mm in diameter and 40 – 50 mm in depth.
It has from 9 to 13 (sometimes 15) eggs in one laying. The eggs are white with slightly bright shell and a large amount of reddish-brown spots and dots which form sometimes noticeable halo at the obtuse end of the egg. The sizes of eggs are from 17x12 to 19x14 mm. The big tomtit has two egg-layings in a year: the first at the end of April or at the beginning of May and the second in June. Tomtits are widely spread in European part of Russia, in Caucasus, at the south of Siberia. It is a settled winter bird.