Avocado and products containing avocado like guacamole are highly toxic to parrots.
Alcohol is toxic to any living being. In any quantity, it kills off stem cells important for regenerating the body and brain.
Chocolate contains the stimulants theobromine and caffeine. The darker the chocolate the more of these stimulants. Chocolate is actually toxic to all animals including humans. An overdose of theobromine can cause seizures, heart failure and kidney damage.
Caffeine in coffee can cause dehydration, seizures, heart failure and death.
Sugar. Parrots are not built to cope with simple sugars found in human foods like cakes and biscuits.
Peanuts (groundnuts, monkey nuts) are likely to contain aflatoxins because they grow underground, unlike tree nuts. Aflatoxins harm the liver.
Onions can irritate the lining of the mouth, oesophagus and crop. They have been proven to burst the red blood corpuscles in dogs. The same may happen to the blood of parrots.
Rhubarb can cause kidney problems because of the high levels of oxalic acid. The leaves are toxic.
Starfruit (Carambola) contains toxins that can cause kidney damage in humans, dogs and cats. It therefore may not be the best choice of food for our parrots too, especially those with kidney problems.
Broad beans (fava beans). In humans, favism is a genetic disorder which results in acute hemolytic anemia after eating broad/fava beans. It may happen with some parrots too.
Cherry flesh and juice is fine to feed (organic is best since they have one of the highest pesticide content). It is the pit that is poisonous so make sure to remove them. Likewise plum, peach, nectarine and apricot stones should be avoided as they, like cherry stones, contain cyanide.
Meats. Animal proteins are mostly high in the amino acid, methionine which is converted into the toxic byproduct, homocysteine, which in turn puts a strain on the liver and kidneys.
Dairy products aren’t toxic but parrots cannot digest lactose. It will manifest as diarrhea. However some dairy products, in small amounts, can be a useful form of calcium. The dairy products with lowest lactose content are plain yoghurt and cottage cheese.
Salt. Birds need some salt, hence gathering at salt/clay licks etc in the wild. But human salt intake is way higher than parrot needs. So be careful. Humans can excrete salt through sweat and urine. Parrots don’t sweat. Therefore excess salt will eventually harm the kidneys. As well as table salt, salt is found in soy sauce, seaweed and commercially prepared foods.
Eggs should be well cooked as they can be a source of salmonella. Refrigerate eggs to halt the growth of salmonella.
Seed only diet is deficient is some of the essential amino acids, vitamins and minerals.
Pellet only diet is deficient in the nutrition a fresh food diet contains, ie. natural vitamins and enzymes.