I just joined and I know it is late...but... I had this also. It was the Lesser Goldfinches! They love the leaves. Luckily it wasn't that big of a deal, they seem to concentrate on one leaf at a time and I don't think that it hurt the plant. They also went after the Strawberry leaves, without much damage, but the Stellar Jays watched the Goldfinches and did it also. Bird Netting is a problem for squash, it stops the pollinators.