The sanctuary sounds wonderful. It is such fun to be somewhere where the birds are nearly tame, and can be safe.
Have you considered putting in some kind of protective covering over a portion of your yard to provide the smaller birds with safe escape and to make it a little less appealing to the hawks?
I have planted a lot of evergreens and other plants for them to hide in but the Hawks are clever. I look out and see them actually hovering over a plant waiting. I put my Christmas tree out there yesterday too. It's a bummer. I feel like I created a buffet. Any other suggestions are so welcome.