WHY BIRDS NEED CALCIUM
By Jim Pearson from Two Wells, South Australia.
An article from Agapornis News, the Newsletter of: The African Lovebird and Foreign Parrot Society of Qld Inc.
Birds, like most animals, need calcium in their diet for bone formation and normal nerve, brain and muscle function. Breeding hen birds require comparatively large amounts for egg formation - egg shells are almost pure calcium carbonate and the egg itself contains calcium which is used by the developing chick.
The parathyroid glands regulate distribution of this vital mineral in a bird's body. During periods of high demand such as egg laying, these glands draw calcium for other parts of the body, including the bones, if insufficient is available from the diet. Calcium deficiency in egg laying hen birds can result in problems such as poorly formed eggs - thin shelled, misshapen and sometimes even shell-less eggs. This in turn may lead to a serious problem known as egg binding, because abnormal eggs can be difficult for hens to pass.
Egg binding is not only due to egg abnormality. It can be caused by the drain of calcium from the hen bird's body during egg formation, which may be responsible for muscle weakness, weakened bones, egg paralysis and occasionally fits. A weakened bird can not successfully perform the strenuous task of laying an egg, especially an abnormal egg.
A low level of calcium in a breeding hen bird does not necessarily manifest itself in abnormal eggs or egg binding. A less obvious (and less serious) symptom is reduced egg production, ie. smaller clutches than she is otherwise capable of. In fact, a hen bird may not come into breeding condition at all if insufficient calcium is available (or able to be absorbed) from her diet. Of course, bird's need a nourishing fully balanced diet, Not just calcium, for breeding success.
Another period of high demand is during the few weeks of very rapid growth. Baby bird's need plenty of dietary calcium to ensure they develop a strong skeletal structure and good muscle tone for that first intrepid flight. Obviously, babies still in the nest must receive this calcium from their parents diet - this is probably why many birds eat the egg shells after their young have hatched.
Insufficient dietary calcium in young birds may lead to splayed legs, beak deformities, easily broken bones or poor feeding response or flying ability due to muscle weakness. These birds often end up dead in the nest or on the aviary floor.
Calcium deficiency may be caused by lack of vitamin D3. Birds need this vitamin to enable them to absorb calcium from the intestine. However, they can manufacture sufficient quantities in their bodies if regularly exposed to natural sunlight. It is therefore normally only birds that are housed indoors that suffer calcium deficiency caused by lack of Vitamin D3.
Poor diet is the more common cause of calcium deficiency in cage and aviary birds, but be aware that poor diet may be due to what the birds actually eat - or more correctly, what they don't eat. Some birds provided with calcium rich foods or supplements may not consume any (or enough) of them. Bird owners must therefore provide their birds with a well balanced diet that will be consumed.
Mark Shephard's brilliant book Aviculture in Australia (pp 20 and 22-23) clearly shows that seeds, vegetables, fruit and live food commonly fed to birds are very low in calcium. The best of them (from a calcium content point of view) contains less than 100mg per 100 grams, ie. less than 0.001% calcium by weight. However, research indicates that birds require 1.5% to 1.8% calcium in their diet prior to and during breeding. They also need calcium when not breeding, but at much lower levels.
It is therefore obvious that in addition to other dietary needs, birds must be fed a calcium rich food or supplement that they will eat, to ensure they get their full requirement of this vital mineral.
How to ensure they get it...
Many years ago bird keepers began supplying birds with shell grit and cuttlefish bone, both rich in calcium and readily digested. Some people supply either home made or commercially available calcium blocks, a good source of calcium for those birds that will eat them. Others make "bird cake" which may contain calcium in the form of egg shells or crushed limestone. (Egg shells must be baked to kill harmful bacteria. Shell grit and cuttlefish bone should be washed to remove excess salt).
However, even when supplied with one or more of the above, some birds still suffer the symptoms and effects of calcium deficiency - why?
Assuming the birds receive adequate sunlight (or Vitamin D3 supplement) it is probable that they do not eat enough of the calcium offered. Perhaps they do not like it; perhaps they gorge themselves on something else (some parrots become addicted to sunflower seed to the exclusion of virtually all other foods). Perhaps it is too big (small birds can't eat coarse shell grit) or presented in the wrong way (some finches don't seem to nibble on cuttlefish bone or calcium blocks - some parrots demolish these "boredom relievers" and may not swallow any). Perhaps the calcium content of what the birds do eat is too low, as in some recipes for bird cake. Perhaps there is not enough variety to satisfy the tastes of all the birds in a mixed collection.
Some bird keepers have overcome these problems by using calcium supplements in the form of liquid (so many millilitres per litre of drinking water) or powder ( a very small number of grams sprinkled on fruit or mixed with seed or dissolved in drinking water). Others use multi vitamin/mineral supplements in liquid or powder form.
These methods can be successful, but may also be expensive, time consuming or forgotten, not to mention the difficulty of measuring the small quantities of supplement required per feeding. Also, some mixtures deteriorate in warm weather and one can't be sure the birds have actually consumed enough (or too much) of the calcium. (Too much calcium can interfere with absorption of other minerals or cause kidney damage).
Some bird keepers ensure their birds get ample calcium by feeding a "calcium grit mixture", ie. a mixture of several coarsely ground calcium rich ingredients.
This method of supplying calcium to birds has proven to be successful. It provides the birds with a variety (ie. choice) of calcium rich substances. Many birds seem to like "calcium food" presented in bite sized pieces, as opposed to whole pieces of cuttlefish bone, for example. It is easy to feed the dry mixture in a small bowl (on its own) and to observe approximately how much is being consumed. The mixture can be left without deteriorating in the cage or aviary for the birds to "top up" their calcium whenever they have a need - and the owner can top up the bowl once a week with a teaspoon or two of mixture. Also there appears to be no danger of the birds getting too much. They seem to instinctively regulate their intake to their requirement. Nothing could be simpler or more effective.