Unmistakable. Dark green (appears black at a distance) above and white below. Wings also dark above and white below, with diagnostic rounded and broad tips. Squarish head profile with striking crest. Winter and juvenile plumage with scaled back, and less contrasting breast band.

Quite vocal, especially in flight at breeding ground. Territorial call: Dry, introductory phrases followed by drawn-out mewing sounds; "wyrrr-peeeoo-weeep". Alarm call "pee-wit".

Flight call:

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