It is very difficult to determine the sex of your companion bird due to the fact that they do not have external genitalia. In fact, most male birds do not have a penis. Some species of birds are sexually dimorphic, with physical differences between the sexes in traits such as feather coloration. For example, male parakeets have a blue cere above their beak. However, many avian species are sexually monomorphic, meaning there is no difference in physical traits between males and females.
Behavior is sometimes used to sex companion birds. If the bird lays an egg, it is a female. You do not need a male present for the female bird to lay an egg.
Your avian veterinarian is the best source in determining the sex of your companion bird. Your veterinarian will retrieve a feather or blood sample from the bird and then submit it to a laboratory for testing. The laboratory will relay the results to your veterinarian, and you will receive a certificate stating the official sex of your companion bird.
Surgical sexing is also available through a veterinarian. The advantages of surgical sexing is that you do not have to wait for laboratory results, and your veterinarian can also examine the bird for reproductive health. The disadvantage is that surgical sexing is more expensive than DNA sexing, and it does cause stress for the bird. Surgical sexing is best performed by an avian specialist.
