Having been an avid bird watcher for 6 years or so now, I know quite a bit about the habits of wild hawks and I hope I can help you a bit. First of all, do you know what kind of hawk it is? I know it will be rather hard for you to be sure as it's a baby and it probably just has down as of now but that would help a bit. Ospreys and Eagles eat a variety of meat including squrriels, woodchucks, smaller birds, and fish. Which of course, I realize you probably don't have access to that type of meat lol. Other hawks generally eat the same thing. Parents feed their babies chewed-up meat. The chew it themselves before they feed it to their babies and feed it straight their mouths. Of course, I don't reccomend this method either because human saliva is posionus to birds(I believe) and that's just really, really gross. I don't really know if beef or chicken would be okay, I'm sure it would, but if you try it make sure you grind it up very well first in some sort of way.

Sorry if I'm not really a help, I try but I've never taken on the task of feeding a wild hawk baby or anything. This is just stuff I know off the top of my head.