The Blue Tit is compact and rounded with a short tail. The cobalt-blue crown and the yellow underparts make it instantly recognisable.
Male - Head: bright blue crown with a white face, black eye-line and moustachial stripe. - Upperparts: olive-green back, blue wings with a white wing-bar. - Underparts: yellow breast and belly, sometimes with a faint dark central line. - Tail: blue with white outer feathers.
Female The female is almost identical to the male but with a duller blue crown and slightly paler yellow underparts. Sexing is difficult in the field.
Juvenile Juveniles have yellowish cheeks (not white) and greenish areas where the adult is blue. They change into adult plumage during the autumn moult.