Thanks for all the suggestions, guys!
1. There is nothing out there to hang CD's from, no trees or bushes or anything. Is why we free range in the afternoons. We have planted a couple of fig trees but they are a ways from providing shade yet. There is shade around the hen house.
2. a. We don't have anything to shoot with; b. neither of us is a good enough shot to hit a moving target (or a stationary one, most likely!); and c. we would never shoot a protected species even if 1 and 2 were not true, game warden or not. Not judging anybody, just saying we wouldn't.
3. If we "criss-crossed" their yard with any kind of tape, twine or string, it would likely inconvenience us far more than the hawk. DH has to get in there to mow from time to time.
My question was: do y'all think the hawk might ultimately move on if we keep our birds confined for a while? And does anyone know how long that might take? Or should I just carry on as always until my flock is decimated?

Am I doomed?