The Blue Tit, Cyanistes caeruleus, is a 10.5 to 12 cm (4.2 to 4.8 inches,) long passerine bird in the tit family Paridae. It is a widespread and common resident breeder throughout temperate and subarctic Europe and western Asia in deciduous or mixed woodlands. It is a resident bird, i.e., most birds do not migrate
Blue and Great Tits form mixed winter flocks, and the former are perhaps the better gymnasts in the slender twigs. A Blue Tit will often ascend a trunk in short jerky hops, imitating a Treecreeper. As a rule the bird roosts in ivy or evergreens, but in hard weather will shelter in a hole. Blue tits are very agile and can hang from almost anywhere.
The Blue Tit has an average life expectancy of 1.5 years.
The Blue Tit is a valuable destroyer of pests, though it has not an entirely clean sheet as a beneficial species. It is fond of young buds of various trees, and may pull them to bits in the hope of finding insects. No species, however, destroys more coccids and aphids, the worst foes of many plants. It takes leaf miner grubs and green tortrix moths (Tortricidae). Seeds are eaten, as with all this family.
An interesting example of culturally transmitted learning in birds was the phenomenon dating from the 1960s of Blue Tits teaching one another how to open traditional British Milk bottles with foil tops, to get at the cream underneath. This behaviour has declined recently because of the trend toward buying low-fat (skimmed) milk, and the replacement of doorstep delivery by supermarket purchases of milk.
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