Carrion Crow (Corvus corone)
Seen clearly it is no contest with the Carrion Crow a much sleeker looking bird than the Rook and without that distinctive beak the Rook has.
There is an old saying and quite a true one; "One or two its a Crow, many more they are Rooks". Carrion Crows can get together in groups but prefer to operate in pairs whereas you nearly always see large flocks of Rooks. Indeed, in terms of life style the two similar looking birds are very different.
The Carrion Crow is, as its name suggests a scavenger; picking at dead carcasses, clearing up people's picnics, harrying other birds who have food to make them drop it, and yes, they do take young birds from nests.
Along the water front, at Baiter, in Poole they are much more successful than the gulls in finding shell fish, flying up in to the air and dropping the shell fish on to the tarmac of the car park to break the shell. The gulls just have not twigged that you break more shells on tarmac than on mud and stones!
Clever chaps crows!