I have a vague recollection of being told a cockie watchman would be wide awake, ear cocked, listening out as well as watching.
That was Liverpool too, late fifties.

Dictionary would back that up

1.1(Of a person) listen attentively to or for something:
she held up a finger for silence, cocking an ear to the background music

http://www.oxforddictionaries.com/definition/english/cock-one's-ear