When I was a kid I remember reading a Ranger Rick article about the smartness of birds, specifically crows and ravens. It said that if the shell of a nut is too hard for the bird to crack, it will place the nut in the path of a vehicle so that the vehicle will run over the nut. It will then collect and eat the pieces of nut. They are also smart enough to pull up unattended ice fishing lines when they see the line moving. They use their beak and their foot to pull up the line then eat the fish off the end of it.
One has only to look at a parrot who learns to mimic the complex variations of the human voice to see how smart birds can be. Not only do these birds mimic such sounds, they can connect meaning to the sounds.
