Olives. Uncured olives contain oleuropein, which is very bitter. If you eat one, the bitterness will linger for hours. This is why olives are cured either by treating them with lye or other pickling process to destroy or leach out the oleuropein (New York Times, Oct. 17, 2007). Aside from their extreme bitterness, there is little evidence that fresh olives are toxic to people.
Found this on the caique site headed Dangerous Human Foods. Personally if in doubt leave it out. That is the rule i live by with my parrots.
In the wild if a bird eats a potentially dangerous food they have access to clay licks that would bind any toxins in the body & they would just pass it in their droppings, but we don't have clay licks on hand for our companions.