I've got a couple of euc trees , acacias, and grevilleas in the backyard and a callistemon in the front. I use the euc (gum) branches in my cages and aviaries for perching, flowers, leaves and gum nuts for shredding. (particularly for the GSC2) The lorikeets get the different flowers for natural nectar and foraging. When the neighbours or myself get fallen branches that are an inch or so in diameter I slice them into rings for toys. The 'tiels love pulling the bark off.

Yes, grevillea is another tree that's good for tiels. It's not as suitable for my local environment as some of the others, though.