Dear Bonnie, There is a box design that can be found at your local Wild Bird Center that has a hole in the top which is covered by a screen. Apparently, the bluebirds do not mind the skylight effect but sparrows do not like it. I have not tried this myself. My only hope this year, after several seasons of emotional bouts with English sparrows killing my baby bluebirds, has been to have a wonderful and licensed friend (who happens to be a naturalist) come over with his 12 gauge shot gun and do away with the last of the killing line of sparrows. "My" bluebirds are now in their third nesting!! Oh Joy! I wish I had done it sooner. Good luck. Katharine Patterson Butler, MD