I recently erected a small bird house/tray which has an overhanding roof onto the garden fence. It turns out to be the local crow population who were cleverly eating the bird peanuts by landing on the bird house and manovering themselves to stick their large pecks into it and gobble. I've thought of putting a little wire around the 4 sides with a small hole for smaller birds, would anyone have any advice on how to deter them in favour of attracting the smaller guys? Thanks.