Healthy adult cockatiels usually weigh 78 to 125 grams. Birds should always be weighed in grams, which is a metric measurement. (There are approximately 28 grams in an ounce.) It is important that a bird is weighed on an accurate gram scale. Electronic scales are available for purchase from bird-supply companies and office-supply retailers. These can be modified by installing a lightweight perch to facilitate weighing birds. A basket may come with some models for weighing baby birds and eggs. Another accurate scale is the triple-beam balance. Serious aviculturists, hobby breeders and pet owners should purchase a quality scale to periodically weigh eggs, babies and pet birds.
Monitoring your bird's weight is one of the easiest ways to keep tabs on its health. Weight change is a very good indicator of a problem with a bird. Weight gain (in an adult bird) may alert an owner and avian vet about the possibility of a bird developing fatty liver syndrome (hepatic lipidosis), fatty tumors (lipomas and xanthomas) or generalized lipornatosis (an abnormal layer of fat deposited under the skin). Weight gain may also be caused by metabolic problems, heart or liver problems resulting in a fluid build-up, problems associated with egg binding, some tumors, lack of exercise or an inappropriate diet.
Weight loss can be a sign of many infectious diseases (including proventricular dilatation disease [PDD], aspergillosis and others), infestation with parasites (including Giardia and roundworms), inappropriate diet, competition for food with other birds, metabolic problems, some tumors and beak problems.
So, weight change should always be brought to the attention of your avian vet. If you have an accurate gram scale, I recommend that you get into the habit of weighing your pet birds on a weekly basis. Weight loss that is not discernable by handling your bird will be documented by the scale long before a bird may become clinically ill and weight loss is obvious.
Just as there are variations in the weights of humans, the same holds true for our birds. Some people are tall and model thin, and, in the industry, Hollywood called some actresses and models "lollipops" because it seems like their heads are too large for their stick-like bodies. This, of course, represents an extreme in body type, but people come in all shapes and sizes. If you have ever checked out the insurance company's weight charts, you'll notice that they have a great weight range for each height on the chart, based on a persons bone structure. While bone structure descriptions are not available for birds, an experienced avian vet will decide if your bird's weight is normal for its size. When I evaluate a bird, I take into account its total length, body structure, pectoral muscling and amount of visible and palpable body fat. I also factor into the equation information from the history regarding the birds diet, cage size and activity level.
When I weigh a bird and give the owner the number, I am invariably asked if this is a good weight for the bird. Because I usually weigh the bird first, before I perform the hands-on physical exam, I cannot answer that question immediately. Once I weigh the bird, then look at it and palpate (carefully feel) the bones, pectoral (chest) muscles, skin and body fat, I can make an assessment about the weight. Deciding if a bird is too thin or too fat is quite a subjective matter, and cannot be simply based on a number on a scale.
Some cockatiels, especially some lutinos and other color mutations bred for the pet trade, tend to be rather smallboned birds. For these birds, a weight between 78 and 90 grams may be average. Cockatiel breeders that are selectively breeding their birds for showing in competition will usually have larger birds. They tend to be longer and more solid in appearance, and often weigh between 110 and 125 grams. I have seen pet cockatiels; that weighed in at a rotund 150 grams. One cinnamon hen comes to mind. She was so obese that she had actual cleavage of the pectoral muscles and a large amount of body fat. By evaluation of her length and bone structure, I estimated that she should have weighed about 125 grams. In the bird world, hens tend to be smaller than males, but, as with all things, there are exceptions.
You can see that you can have the cockatiel equivalents of Laurel and Hardy. There are many different body types and weights, with some that need to be monitored closely so that they do not gain too much weight. It is very important that you establish what is a normal weight for your pet birds. An accurate gram scale is an important piece of equipment for the serious bird owner. As an alternative, many avian vets will weigh your birds for you at no charge or for a minimal fee. You will just need to be diligent enough to bring your bird into the clinic periodically for its weigh-in. Either way, monitoring your birds' weights is easy and could save their lives by allowing early diagnosis of many medical problems.