Jackdaw

Corvus monedula

Jackdaws are smaller than Crows and have a mostly grey head, a dark grey front and distinctive light/white eyes. Often seen in pairs, they have a strong pair-bond.

They are gregarious birds which spend much of their time high in trees or on high buildings. They often nest high on churches, cathedrals and similar; also on cliffs.
The flock ("clattering") has a strong social hierarchy. Jackdaws will occasionally carry off and hoard shiny material/objects, as magpies do.

 Links:

Carrion Crow

Hooded Crow