-- Kathleen E. Davis, Cedar Rapids, Iowa

When it comes to determining sex in psittacines, there are two groups of species: dimorphic and monomorphic. In species that are sexually dimorphic, the two sexes can be determined by different coloration or pattern of feathers. In species that are monomorphic, the sexes have the same feather coloration or pattern, making it impossible to use these characteristics to tell them apart.

Cockatiels are dimorphic. Female grey, lutino and even albino varieties have yellow bars on the underside of the retrices (tail feathers) and yellow brush marks on the underside of the primary flight feathers; on males, these feathers are solid. However, not all varieties of cockatiels are easy to tell apart. It's difficult to see the bars and marks on some of the genetic crosses such as pearlies because both sexes are so mottled.

A few other species also are easily sexed. For instance, in the budgerigar, hormones influence the color of the cere, the fleshy part of the face surrounding the nostrils. Male hormone turns the surface tissue bright blue; female hormones turn it brown. The princess parrot (also known as Princess of Wales) is easily sexed by the shape of the outside flight feather. The tip of the male's feather is spoonlike instead of tapered. Eclectus parrots are the easiest to tell apart: males are green and females are red and purple.

An obvious way to tell your bird's sex: eggs. Single layers are, of course, female. Pairs that produce fertile eggs must be two opposite sexes - but without carefully observing who's doing the laying, it's not always obvious which are which.

It was once thought you could determine the sex of a cockatoo by eye color; however, this has proven untrue.

In most species of parrots, you have to determine sex by some other means. One sure-fire method is surgical. The veterinarian uses gas anesthesia to put the bird to sleep, then makes an incision in the left side and inserts a scope to identify the reproductive organs: in females, a single ovary that looks like a small cluster of grapes; in males, two testes, shaped like beans. The advantage of surgical sexing is that it's 100 percent accurate and allows the veterinarian a look internally, useful in cases where there is a question of reproductive capabilities or other organ problems. On the negative side, it is surgery, involving anesthesia (although a small amount) and entering the body cavity through the skin and body wall with a slight risk of hemorrhage.

DNA sexing, performed by examining the DNA obtained from a blood sample, is your other option. Performed at a lab with high standards, quality control and competent technicians, DNA tests on a blood sample taken from a vein by your veterinarian gives you results close to 100 percent accuracy. As a plus, DNA sexing isn't invasive and doesn't require anesthesia.

While there are now labs that offer to perform DNA sexing on feathers, I don't recommend it. Pulling your bird's feathers hurts (as does clipping a toenail too close to obtain blood) and you can damage the follicle, resulting in a cyst or permanently deformed feather.

James Harris, DVM is owner and medical director of the Mayfair Veterinary Clinic in Sandy Bay, Tasmania, Australia. He founded Montclair Veterinary Hospital in Oakland, Calif., and has served as medical director and chairman of the board for the International Bird Rescue Research Center in Berkeley. Dr. Harris' numerous professional honors include California and National Bustad Companion Animal DVM Awards.

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