Crows mainly eat carrion, garbage, and vermin, so even I would rather not think about what they eat. Lewis seems much more refined than other crows, but his diet remains about the same. Of course, as has been shown previously, he does quite enjoy many types of wild berries, as do most crows. Really, crows will eat pretty much anything, so their food could come from pretty much anywhere. Not thinking about it is the wisest choice.