The Rook can be distinguished from the Carrion Crow by its large, light grey beak and barer face; it is also not as sleek, often with shaggy feathers on its belly giving it an angular shape.
It is gregarious, found in flocks and roosting in rookeries of many nests in neighbouring trees.
Typical bare grey beak and shaggy, angular shape
Adult Rook (left) with bare grey beak and untidy, angular appearance and two young Rooks which look like Crows with sleeker shape and feathered top of beak (which they lose later)
Rook size comparison with two Jackdaws: bigger bird and beak but smaller head