Foraging for 'Tiels

What foraging setups/toys does your 'tiel like? I sense Blanco lacks ambition, so to date I've done nothing more complex than move his "fruity pebbles" aka pellets around the cage. Scotty will handle some of the more complex toys, although he'd rather bash than think, and Scooter will work the cardboard box ones, but has little patience for solving puzzles. Can a tiel beak get through cardboard OK? Compared to Scooter he seems rather delicate, despite being almost twice his weight!

If it interests them, yes, they can easily go through cardboard. I have wood molding covered up so Sam the tiel can't eat the molding. It just has to interest them - which is a whole nuther issue.

Mine "eat" 4 ft long perches down to nothing in a week. Don't think cardboard would slow them down for long if they decided it was fun. Have you tried the little cat toy balls?

We do things like wrapping whatever treat/food/toy up in paper or for more fun, corn husk. Mali loves pruning the silk off corn too (infact corn cooked in it's husk and then put in, with or without the edible bit is a favourite in our house).
You can wrap things up in rice paper rolls and bake them till they're crispy? Mali goes nuts for anything flaky and crispy like that.
Definitely cardboard boxes will work a treat, I've seen people use confetti in a bowl and add beans or seeds or something?

Is corn silk OK for them to have? I have tended to worry they might ingest it and impact the crop. I'll be less anal about removing it if that's an unnecessary concern!

Granted Mali tends to just make it give her scritches ...

Those little paper chinese finger traps are really popular with Einstein.