I am a subscriber of a very good yahoo group called Feeding Feathers. We have just been discussing the issue of prepared human foods in the diet of parrots. The lady who raised the question is from the UK and her parrot started picking on his foot till it bled. All tests were done but nothing serious was found. They went to another vet and he found the cause of the problem - salt! Salt, which has been accumulated in her African Grey's diet over the years, as a result of her giving him an OCASSIONAL (!) piece of sausage, meat, this and that table food, lead to the kidney toxicity. Because the kidney put pressure on his foot he started picking on it.
In Avian Medicine. Principles and Applications salt and as its carriers - crackers, chips, prepared food are listed among other toxic compounds. The consequences of salt toxicity are : gastrointestinal irritation, depression, weakness, death. (all according to the clever book).
When talking about salt toxicity it is not implied that a large amount of salt is consumed over a short period of time. It can get accumulated in the body over the years and lead to all the problems listed above. In addition, all table prepared foods, junk food, biscuits, cakes and meat are rich in saturated fats. These lead to very high cholesterol levels in parrots and as a result - heart attacks. I have heard of cases of very young parrots dying suddenly of heart attacks.
If you want your companion parrot to live its life to the full, up to an old ripe age please don't feed any table foods! Don't think that parrots are like children need to be spoiled on times. It is not the same! Spoil with a lovely almond in shell, a piece of birdie bread, a grape, but not with human table and junk foods.
All the toxins consumed by parrots (salt, sugar, excess fat, chemicals, preservatives, etc.) are removed by the two main detoxifying organs: liver and kidney making these two organs very susceptible to failure if the diet is all wrong.
Please remember chocolate, coffee, avocados, crisps, salted nuts, sugary sweets, like Haribo can and will kill your bird so please don't feed any of those things to your parrot!!!
Here is a link to one of the threads describing how sick a damaged liver can make a parrot
http://www.africangreyparrotcentre.co.uk/african-grey-forum/african-grey-diet/dramatic-liver/msg158059/?topicseen#new