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.
This species was first described by Linnaeus in his Systema naturae in 1758 as Parus caeruleus. Most authorities retain Cyanistes as a subgenus of Parus, but the British Ornithologists' Union treats Cyanistes as a distinct genus. This is supported by mtDNA cytochrome b sequence analysis which suggests that Cyanistes is not only distinct, but not close to other tits (Gill et al., 2005).
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