Injured baby magpie

[Zebrulous]

I work at a vet clinic, I am a vet tech student, and today someone handed in a baby magpie. I am guessing it's a fledgling around 3 weeks old, it can flap its wings but not fly. I have looked it over and couldn't find any fractures nor signs of internal damage, although it has a wound on its head and seems pretty concussed. It however seems alert of its surroundings, but prefers to just lie down. Can stand and use all digits, frequently stands up to do a big stretch and will stand on my finger like a perch. can flap its wings nicely. But it will not eat! I bought it some crickets as this was the only thing the local store had, but I will also go out and scavenge for some natural insects from our fauna and see if he wants those. What do you suggest I do if I can't get him to eat? Worst case I'll need to force feed him! (I have experience with hand feeding, but am very worried about the lack of feeding response and him aspirating...) I have already had him for almost 6 hours now and still can't get him to eat. The local wildlife etc. rehab can't take him in at the moment but were delighted I wanted to try to help him. What do I do, does anyone have experience with this they would like to share? His wound is being treated, everything other than the anorexia is fine!