I was wondering why avocado is toxic to birds and did a little reading on the subject.
Avocados are toxic to birds and other animals because of a fungicidal toxin called Persin, similar to a fatty acid and present in the bark, twigs, leaves, skin and pit.
Apparently some birds have survived after eating avocado, but definitely not worth the risk!
The side effects in birds include increased heart rate, myocardial tissue damage, labored breathing, disordered plumage, unrest, weakness, and apathy. High doses cause acute respiratory syndrome (asphyxia), with death approximately 12 to 24 hours after consumption.
Don't feed avocado to any of your pets!!
Sources:
http://www.goodstuffbirdfood.com/?p=80
http://en.wikipedia.org/wiki/Persin