We researched many potential grape covers and there are some that both protect against birds and insects and let sufficient light through (over 90%) but we discovered a locally designed cover through Kootenay Covers
Kootenay covers makes covers for grape vines and fruit trees and their product protects from birds and insects and lets signifiucant light through. I don't have figures on how much light goes through this product but it is substantial and I'd estimate between 85%-95% of the light goes through.
One of the hopes with this product is that it may provide a small degree of frost protection at the end of the season. Even 1 degree of frost protection can make a huge difference in staving off that first frost and allowing the grapes to ripen perhaps another week.
We deployed the netting in late August and did some preliminar tests on the overnight temperature profile between the covered row and the uncovered row beside it. We checked the temperatures hourly after sunset until about 11 pm / midnight and found that overnight lows were the same for the covered row and uncovered row except that the neeted row stayed warmer (1-2 degrees) longer into the night then drops off fast and equals out to the uncovered row after 11pm.
We'll do some more testing as the frost season approaches and report back. So far we really like the covers. They appear to be very durable, easy to deploy and the cost was significantly less than other similar products. Check out this link to Kootnay Covers.