Finally, I think I may have defeated the crows.

I always wanted to put a roof on this tray feeder to keep the crows
and snow off, but I didn't want to shade it so we couldn't see the birds.

After a trip to the Iroquois NWR a couple of weeks ago, I noticed
they had made a roof similar to this. Using scrap cedar and two
pieces of polycarbonate that I bought, I built my own.