While many parrots exhibit color or size differences between males and females, determining the sex of lorikeets by sight is difficult. Both male and female lorikeets are brightly colored; both range from 6 inches to 16 inches long. However, there are several other reliable methods for sexing lorikeets.
Watch for Mating Behavior
It may be possible to tell males from females during mating season, when males put on a show to attract females. For example, the male rainbow lorikeet will hop around the female, stretching his body out to full length, extending and bobbing his neck. He will often emit a low whistle at the same time. Sexing this way requires patience, because lorikeets don't mate until they are at least 18 months old.
Check the Nest Box
It may sound obvious to say that only female lorikeets lay eggs. But if the birds use a nest box, both the male and female will spend time in it, so it may not be possible to know which bird laid the eggs. After laying the eggs, however, the female stays and sits on the eggs. The male leaves the nest box.
Send for DNA Testing
Many labs will determine a bird's sex via DNA testing with a sample of a feather, blood or egg shell. Pluck fresh feathers for this purpose; don't use fallen feathers. Choose egg shells from recently hatched chicks and be sure they are not tainted by other materials or birds of other species. Taking blood samples can be painful and dangerous to the bird, and feathers and shells provide equally reliable DNA samples. DNA testing can be performed on birds of any age.
Ask a Veterinarian
Even an avian veterinarian won't be able to discern a lorikeet's sex on visual appearance alone. A vet can perform a surgical procedure called endoscopic bird sexing. After anesthetizing the lorikeet, the vet places an endoscope into the air sac in the bird's abdominal cavity, where the sex organs are visible. Endoscopy is invasive and carries risks of complications and infections, and is more expensive to pet owners than DNA testing.