okay searching as I do I came across this website which has case studies stating that Budgie hae a preference to which Gum tree they prefer ....

 

HERE IS THE LINK

Not surprising when you think about it. There are different types and levels of oils and different textures present in all eucalypts. I try to get a few different varieties when I collect for my birds. I can recommend lemon scented gum which is commonly planted in nature strips, etc as it doesn't get too massive. It can be easily distinguished by a lemony smell and is also nice if crushed in the hands and added to a pot of tea while it steeps (especially if you have a cold) It is fast growing, and low in tannins, etc just as suggested by the author of that study. The leaves are also not too tough which my birds seem to avoid......good find Neat

I haven’t had time to read it yet…but looks like a good find Neat thanks.

well the Koala only eats one or two types.