Blake Hawley, DVM
Birds are curious creatures. It seems that there is a conspiracy among them to do whatever we want them least to do. Take eating for example. How many times have you placed a nutritious morsel in your bird's dish, a succulent vegetable tidbit, or juicy fruit treat, only to see your bird appear terrorized by this harmless and healthy treat? Oh, but let that bird choose its dinner and watch in amazement as everything in sight becomes a possible treat, whether its that plastic apple on the coffee table or the candy bar you had been saving for after dinner. Why birds seem to have a predilection for getting into things they shouldn't is a mystery, but preventing these possible catastrophes isn't.
There is a considerable amount of anecdotal information available from aviculturists, breeders, and hobbyists reporting observations on different foodstuffs, however, valid, scientific evidence is less numerous. It is wise to assume that any food or agent that is harmful for dogs, cats, or people is also harmful to birds. Unfortunately, birds appear to be much more susceptible to toxins than mammals. This increased susceptibility to toxins may be due in part to their smaller size, rapid metabolism and unique physiology.
A growing concern for birds that is not related to toxic foods or agents found in foods is the practice of feeding table scraps. A common belief is that if birds eat people food, they will receive a good diet. Unfortunately, this is generally not the case for the following reasons. People generally do not eat healthy. The incidence of heart disease, cancer, and obesity in Americans is certainly due in part to poor dietary habits. While many people begin feeding their birds nutritious foods, these good intentions often decay into fatty, salty, fast food items. Even people who provide a well balanced table diet to their birds cannot guarantee consumption of all the diet provided. As with almost any diet, what is placed in front of the bird is not necessarily what it consumes.
Further, if a bird consumes a food which is high in calories, it may not be able to eat enough food to be properly nourished. Birds, like all animals, eat to meet their energy requirements. A single food source, provided in sufficient quantity, may provide a bird with its daily energy requirement, while depriving it of its daily nutrient needs. An example of this principle is a cookie. A single cookie may contain as many as 200 calories, or roughly the entire daily caloric requirement for a macaw!
Another problem with table scraps or human foods involves bulk. Birds are very small animals. Giving a parrot half an apple is equivalent to a person being given a ten pound head of lettuce to eat. Many foods, fruits especially, are high fiber foods, which may fill up the crop, proventriculus and ventriculus and lead to satiety (the state of being full, not hungry). Again, foods which contain high fiber or are high bulk, may fill the bird but not provide adequate nutrients.
Given then, certain "nutritious" foods are not necessarily good for your bird. Foods must be provided in the appropriate amounts and must be balanced for energy in an overall dietary scheme. Some foods however, should be avoided in any quantities.
Chocolate is a highly palatable food. Some of us know that all too well. Unfortunately, many birds seem to love chocolate almost as much as people. Chocolate is not bad for birds just because it is high in calories and fat though, it contains a compound called theobromine. Theobromine is toxic to dogs and cats as well, but birds, again due to their smaller size and more rapid metabolism, may be even more susceptible to its toxic effects.
Generally, the sweeter the chocolate (more sugar), the less theobromine present (milk chocolate contains about 1-2 mg of theobromine per gram, dark unsweetened chocolate may contain as much as 15-16 mg per gram). Despite this, no chocolate should be given to birds. Signs of chocolate toxicity include: hyperactivity, vomiting, diarrhea, heart arrhythmias, seizures, dark colored droppings and death.
Another item of concern in birds in sodium chloride, or salt. Salt, however is required by birds as it is by all living animals. While minerals, such as sodium and chloride only constitute a small fraction of the body weight, they are critical for a variety of functions within the body including acid-base balance, maintaining body fluid balance and many general cellular functions. A deficiency of sodium can cause polyuria (excessive fluid excretion), weight loss, fatigue, and slow growth. Many otherwise healthy foods that people routinely eat are high in salt. Further, many crackers, snack items, chips, fast foods, and canned vegetables (unrinsed) if eaten in sufficient quantities may actually be toxic to birds.
Signs of a mild salt toxicity (5-10 times requirement) will result in polydipsia, or increased water consumption and subsequent polyuria, or increased fluid (urine) in the droppings. Because excess salt is excreted via the kidneys, a bird with mild to moderate kidney dysfunction may consume toxic doses of salt readily. Deprivation of water alone may lead to salt toxicity because the kidneys are not proficiently perfused or bathed by fluids to remove the sodium and chloride.
Even birds with good kidney function may develop signs of a toxicity if salt is consumed in large quantities. Besides polydipsia and polyuria, a toxic insult of salt may lead to kidney failure (with no urine produced), a subsequent build-up of body fluids (ascites), neurological signs2 and heart failure leading to death. Poor growth and feathering is seen in babies fed too much salt, such as provided by hand feeding diets with high sodium peanut butter.
Alcohol may seem an obviously harmful substance, but some people do not realize that even small amounts may cause harm in birds. Many birds which were fed alcohol died by accident while "flying under the influence." Even placing alcohol on open wounds may result in absorption sufficient to cause depression, incoordination and regurgitation. While small quantities of alcohol appear to be good for the cardiovascular system in people, this is not true for our feathered companions.
Other common human foods sometimes fed to birds may cause problems. A prime example is avocado. In both clinical experiments and numerous anecdotal reports, avocado ingestion caused irritation and excessive preening. Other reports have included a cessation of eating, rapid short breaths and death. Parsley has often been reported as toxic in birds, but it has only been shown in ducks and ostriches to cause a sensitivity to the sun. No evidence exists to show this effect in pet birds, and many diets contain small amounts with no harmful effects. Onions were reported in one article as poisonous, although other references to this were not found.
Very often, when birds are found suddenly dead, the food is the first thing blamed, most often because beginning bird owners are slow to recognize the subtle signs of illness in their pets. However, common foods that are normally healthy or at least non-toxic, may be the cause disease or death if the food itself has become contaminated. The most common types of contamination are by pesticides, bacteria and mycotoxins.
Most vegetables, fruits, and produce that we buy in the grocery store have been sprayed with pesticides at some point in their growing cycle. Even organically grown foods may be unscrupulously sprayed by vendors. The best way to prevent toxicoses by pesticides is to thoroughly and completely wash and scrub fresh foods before giving them to your bird. Cases of pesticide poisoning are very difficult to diagnose.
Another, more common cause of contaminated food is bacteria. We know bacteria are ubiquitous (they are found everywhere, no matter how well you clean), but certain conditions predispose very high numbers of bacteria. Foods containing high amounts of water or foods soaked in water (seed, monkey chow) should be fed very carefully to birds. Often soaked foods contain a tremendous number of bacteria that can overwhelm your bird's immune system, in fact water and high water content foods are the number one cause of high bacterial exposure in pet birds.
The other cause of contaminated food is mycotoxin tainted food. Mycotoxins are chemicals produced by certain varieties of molds and fungi. Often, the mold or fungi is no longer visible when the toxins are ingested, so these toxicities too are difficult to spot, but food can be tested for the presence of mycotoxins. The most common mycotoxins affecting grains are aflatoxin, ochratoxin, vomitoxin, and T2 toxin. These toxins cause clinical signs that include anorexia (not eating), depression, sores in the mouth, toxic liver changes, kidney failure, and rapid death.
Mycotoxicoses are easily prevented by feeding only high quality, clean seeds and grains or better yet, an extruded or manufactured diet (which is much less likely to contain mycotoxins because of the cooking process and the lack of moisture). The most commonly implicated foods with mycotoxins are poor quality peanuts and peanut butter, breads, meats, cheese, and grains. If a food smells moldy or certainly if mold is seen, the food should be discarded and not fed. Seed products which contain bugs, such as grain beetles or meal moths, should not be fed (it is unlikely that the bug itself would harm a bird, they certainly consume them in the wild, but the damage the bug does to the seed hull makes it more likely to be less nutritious and increases the possibility of contamination).
Though the list of harmful foods may seem ominous, if clean, well stored foods are fed to birds, they very rarely develop food toxicoses. Any food should be kept in a cool, dry place, preferably in an air-tight container or zip-lock bag. Soft, moist foods or foods soaked in water should generally be discarded after about four hours in the cage. Food items which are not healthy for birds should be removed from their reach. Despite the fact that certain chemicals, such as organophoshates, are much more toxic in birds (these are fairly easily avoided), they appear much less likely to develop food related illnesses than mammals.