Margaret A. Wissman, D.V.M., D.A.B.V.P. wrote this regarding onions, leeks, garlic, and chives:
"Allicin, which gives garlic its odor, is also a strong oxidant. In rare cases, this chemical can be dangerous and can cause Heinz body hemolytic anemia, as well."
"Although I have not seen any scientific studies performed on any avian species, there is the chance that disulfides could also cause this Heinz body hemolytic anemia in birds. For that reason, I feel that is unnecessary and potentially dangerous to feed onions, leeks, garlic or chives, as they don't contain any nutrients that are vital for the health of our pet bird. Why take the risk?"
Source:
http://www.exoticpetvet.net/avian/onions.html
"Allicin, which gives garlic its odor, is also a strong oxidant. In rare cases, this chemical can be dangerous and can cause Heinz body hemolytic anemia, as well."
"Although I have not seen any scientific studies performed on any avian species, there is the chance that disulfides could also cause this Heinz body hemolytic anemia in birds. For that reason, I feel that is unnecessary and potentially dangerous to feed onions, leeks, garlic or chives, as they don't contain any nutrients that are vital for the health of our pet bird. Why take the risk?"
Source:
http://www.exoticpetvet.net/avian/onions.html