Old CD's hung up around the garden can scare off the birds with the way the sun light glints off them. We were using large bottles to protect some of the seedlings when we first put them in, helped stop the snails and in the cooler weather acted like a mini green house. Now we are not using the bottles we have stuck them on the top of some the stacks around the garden and have found the noise they make when they move in the wind seems to also keep the birds away as well.