The tawny smell isnt diet related, they just smell.
Their poo smells just as nasty, regardless of what you feed them.
They love mice, but if you give them too many then they will get fat, but if you just feed them on oxheart and insectivore mix then they will probably lose condition.
Often when they are in from the wild they wont eat food unless you put it in their beak. Pain in the bum when you have 20 of them in care!
Your aviary may need some shadecloth to cover the wire, they they have different eyesight to most birds, and will keep flying into the wire if they arent used to it.
I would recomend a HUGE aviary if you are keeping them permanantly. And i dont see the point in keeping a perfectly good bird captive. Please only take on un-releasable birds.