Who's that tapping?

Sometimes when I walk quietly round the garden I hear a tapping coming from one of the far corners. It is another of the gardeners friends, a Song Thrush. We have a real problem with the number of snails in the garden and this chap is one our side. He (or she) normally finds a suitable stone to use as an anvil and the area around it is littered with snail shells. The only problem we have is too many snails and not enough Song Thrushes. His song is one of the earliest as the dawn chorus starts, it's a good song and he repeats each phrase, normally three times to make sure you've heard it.