Diagnostic combination of blue crown, and yellow belly makes it easily recognizable. No white tail-feathers. Sexes similar, but male slightly brighter blue. Juveniles paler than adults, with greenish crown and yellowish cheeks. One of the smallest of the tits.

Song: Characteristic, clear, high-pitched, vibrating call. Usually introduced by a couple of accenting syllables, followed by ringing vibrating notes: "ti ti chuhuhuhuhuhuhuhuhuhu". Scolding alarm call: "tee-tee-tee-chirruwitt" similar to Great Tit.

Song:

Wikipedia: map (se also Xeno-canto below)

Birdlife ecology

Observation.org Latest observations

Video IBC

Image search Flickr NB! May give other species

Sound search at Xeno-canto

Featherbase