The Eurasian Blue Tit (Cyanistes caeruleus or Parus caeruleus) is a small passerine bird in the tit family Paridae. The bird is easily recognisable by its blue and yellow plumage, but various authorities dispute their scientific classification.
Eurasian Blue Tits, usually resident and non-migratory birds, are widespread and a common resident breeder throughout temperate and subarctic Europe and western Asia in deciduous or mixed woodlands with a high proportion of oak. They usually nest in tree holes, although they easily adapt to nest boxes where necessary. Their main rival for nests and in the search for food is the much larger Great Tit.
The Eurasian Blue Tit prefers insects and spiders for their diet. Outside the breeding season, they also eat seeds and other vegetable-based foods. The birds are famed for their skill, as they can cling to the outermost branches and hang upside down when looking for food.
The Eurasian Blue Tit is usually 12 centimetres (4.7 in) long with a wingspan of 18 centimetres (7.1 in) for all genders, and weighs about 11 grams (0.39 oz).
A typical Eurasian Blue Tit has an azure blue crown and dark blue line passing through the eye, and encircling the white cheeks to the chin, giving the bird a very distinctive appearance. The forehead and a bar on the wing are white. The nape, wings and tail are blue and the back is yellowish green. The underparts is mostly sulphur-yellow with a dark line down the abdomen – the yellowness is indicative of the number of yellowy-green caterpillars eaten, due to high levels of carotene pigments in the diet. The bill is black, the legs bluish grey, and the irides dark brown. The sexes are similar, but under ultraviolet light, males have a brighter blue crown. Young Blue Tits are noticeably more yellow.
There are currently around 20–44 million pairs in Europe. The Eurasian Blue Tit and the related hybrids are considered native species in areas of the European continent with a mainly temperate or Mediterranean climate, and in parts of the Middle East. These areas include the United Kingdom and most of theEuropean Economic Area (except Malta, where they are considered vagrant, and Iceland, where they are absent), plus: Albania, Armenia, Azerbaijan, Belarus, Bosnia and Herzegovina, Croatia, Georgia, Iran, Iraq, Jordan, Kazakhstan, Lebanon, the Republic of Macedonia, Moldova, Montenegro, Russia, Serbia, Switzerland, Syria, Turkey and Ukraine.
Eurasian Blue and Great Tits form mixed winter flocks, and the former are perhaps the better gymnasts in the slender twigs. A Eurasian Blue Tit will often ascend a trunk in short jerky hops, imitating a Treecreeper. As a rule the bird roosts in ivy orevergreens, but in harsh winters will nest wherever there is a suitable small hole, be it in a tree or nesting box. They are very agile and can hang from almost anywhere.
This is a common and popular European garden bird, due to its perky acrobatic performances when feeding on nuts or suet. It swings beneath the holder, calling “tee, tee, tee” or a scolding “churr”.