pinkfreud, it looks like Atticus survived by eating all the other baby birds. He’s a round little guy!
Mama Zappa, how well feathered is your found baby bird? In particular, are his primary flights developed? Does he try to fly, and how well, when you approach?
Often they go through a stage where they’re learning to fly, but not very capable yet, and you’ll find them on the ground looking lost or cranky. I think they come up to speed very fast though.
If nothing can get at him in the garage, and you’re not using it, I’d put a shallow plate of water (something he’s unlikely to drown in) and some seed (or in an emergency, bread crumbs) near him and leave him alone.
Caveat: I know that different kinds of birds eat different things, and he might not be a seed eater, but we’re talking emergency measures that might help. I don’t expect anyone to masticate some bugs and regurgitate for him.
I wouldn’t take him into custody unless he looks really too young/undeveloped to fly, or seems to be getting weaker.
Meanwhile, do try and talk to a wild animal rehabber; he or she will be much more knowledgeable than I am.