So long as they have contact with dirt or some grit (play sand works fine) then if they'll eat it, it's fine.
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There's a reason for that. Most of that stuff is known to be harmful to dogs but no studies have been done on birds so it's largely unknown just how harmful they are. I've heard of more than one pet bird mysteriously dying after being fed chocolate though so that's why I'm so animate about that one.
Edit: I got this information from my Avian Vet, so far as the "no studies" thing. I asked her after I was unable to find any information about onions being toxic. Come to find out, no studies have been done on birds for just about any of this stuff.