I don't know what he is. He's not a duck, doesn't have webbed feet. He does look like a water bird though. If he can move this morning I'd take him back to where you found him and release him back. If he's still not moving I'd call the conservation department.

If you didn't feed him anything last night or if you did and he didn't eat don't worry, it was late and birds don't eat at night (unless they're nocturnal, which he's not). This morning you could soak a little dog food in water until it's spongy. Just lay it the tub with him and leave the room. He may or may not eat it.