I use plants in pots in the aviaries. I bought a few, one was from the "Butterfly" section of the nursery - "Milkweed". Figured if they were safe for butterflies, they would be ok for birds.
NOT!
Thankfully, did research before putting it in the aviary.
The milkweed is like candy to the now endangered monarch butterfly. One of the reasons is, the milkweed makes them taste bad to birds. So - the plant, sap, flowers and nectar is not 'toxic' per se, but an extreme irritant to birds.
Lesson learned - and again I apologize for the repeat, but here is a list of 'good and bad' plants for birds/aviaries. There may be more complete lists, but this is what I found with a quickie search. Headed out to take my sister to the airport.

http://www.birdchannel.com/bird-housing ... lants.aspx