Hard boil some eggs and chunk them up with a fork or a pastry cutter. Make some oatmeal -- don't add fat, salt or sugar, just oatmeal. He can peck at unseasoned vegetables, but to be safe, stay away from potatoes, tomatoes, and eggplants. Nothing with salt, sugar, chocolate, or onions. Cooked beans or rice are okay, but not dry beans or rice. Avoid avocado and dairy. Fruit is okay, but no citrus or apple seeds. Cooked meat -- including chicken -- is okay, but sparingly if there is a lot of seasoning on the meat. Chickens love meat so you could brown some hamburger -- no seasoning. If you're having turkey for Christmas dinner, give him the bones to pick clean.
It's not great for a steady diet, but it should hold you for a few days. Make sure he has plenty of fresh water.