Unmistakable, if not in silhouette. In poor light or at a distance, when the grey plumage is not visible, confusion with other crows is possible. Bill is deeper than in Rook, and the upper mandible more curved towards the tip. Smaller than raven, and much less heavy bill. The wings are shorter and more rounded, and the tail is not wedge-shaped. Posture less upright than Rook.

Cawing is aggressive and more raucous than in Rook, with more rolling r's. Has a large repertoire of seldom heard calls, and even sub-song. Many of these calls are surprisingly resonant and pleasant sounding, and sometimes resembles Raven. Probably impossible to tell from Carrion Crow with certainty by sound alone.

Cawing:

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