I'm wanting to put a living plant in my aviary. I'm thinking something like a bottle brush, or other grevillia. Are these safe for budgies, finches, cockateils and grass parrots? Or what other tree or shrub can I use? I just think it will make the aviary look a whole lot nicer, and I'm sure the birds will love it.

Well I give mine bottle brush branches and most natives and trees of the gum family are safe. It would have to be a largish tree (mature would be a better word ) and best in a pot for budgies usually strip trees bare so you would have to remove it once in a while so it can regrow.

i give mine native tree branched and NON-SPRAYED branches from my fruit trees

We put native tree branches in our aviaries too. I think one of my hens was actually craving eucalyptus the other day, as she was foraging dried leaves, so we put some fresh eucalypt in there and they love it. The oil in eucalypt is very beneficial too.