Messenger Pigeons/crows - GoT

[kcdusk]

My father in law races homing pigeons. You take the pigeons anywhere, release them, they come home. Back in the day you could attach a message to them and deliver hand written notes.

Watching Game of Thrones the other night, i noticed they were using crows to do the same thing.

Have crows ever been used this way before? Or is Game of Thrones not historically accurate?