Question
Stephen,

Do you know how to keep crows out of a garden? I've seen foil pie plates attached to the fence, maybe that works with the noise they make?  

Thanks

Answer
Exclusion is the best method, suspending netting or wires over the garden.

Next would be some sort of hazing to help reinforce the frightening devices you may use. Shiny objects, things that move, even owl effigies can help. But with the owl effigy, move it every couple of days.
Methyl anthranilate fogging will also work but you may not want to spend the money on it.
More details can be found at http://icwdm.org