Cockatiels have two different genders, males, and females. Female is the sex that carries eggs; the male is the one to fertilize the eggs. At times you can also hear the words cocka and hen to be used of the cockatiel male and female.
The male is the more colorful one. The primary color of the plumage is grey, tone differing only very slightly individually. The upper side of the tail feathers is silvery pale grey, and the lower side is dark grey, almost black. There are altogether 12 tail feathers, and the middle ones are the lightest ones. The upper rump is a bit lighter than the rest of the body, whereas the wings and back are darker. The head is the brightest part. Male has a yellow face mask reaching the root of the crest that turns greyish towards the tips of the crest feathers. Precisely on the ear whole, there’s an orange-red cheek patch.
The female cockatiel has clearly more greyish face than the male does. The yellow mask and red cheek patch are softly covered with a thin layer of grey. The clearest difference to males besides the covered face mask is a striped pale yellow pattern of the female’s tail. Taking a closer look, these stripes are not really clearly formed. More likely, there are tiny teardrop-shaped black areas on the pale grey surface. The yellow parts are widest and clearest in the edge tail feathers. Opened wing of the female also shows spot markings: there are 3 to 6 light spots on the primaries and secondaries.
Both sexes have grey beak and legs, black nails and brown eyes.
They are around 28-33 cm tall; the tail is around half of this measure. Wing length of the cockatiel is about 16-18cm. Wild cockatiels would have a crest size of 4 to 6 cm, but captively bred cockatiels have at times even more than 10 cm. Wings have a long white patch that looks like a triangle as the wing is opened. This patch serves a purpose of helping keeping contact to the other flock when the cockatiels are flying together.
When young, all the cockatiels resemble females. When they reach the puberty, the males start to produce more melanin – dark color pigments – reaching a colder tone to their plumage. They will also drop the grey facial feathers and striped tail feathers that are replaced with the yellow face mask and dark, simple feathers. This normal wild-type color reaches the final coloration at about the age of nine months, but many color mutations might affect the time that these changes take.
Males are known to be the singers of this species. They have several voices to whistle, and often the whistles are individualistic. On the other hand, males can also easily mimic other cockatiel sounds, and this way learn the even wider scale of sounds. The greatest meaning of singing is to charm females, but sometimes it seems that the males are singing just for fun or practice. Males can also click their beaks, keep this harsh growling sound and do many other sounds. At the age of 11-13 weeks, the cockatiel males will start to practice their singing skills. Each male seems to mix their own tones to the song even if they took some parts from their fellow cockatiel cocks. Also, improvisation seems to be common with enthusiastic singers. When the male is proposing the female, it chirps and does these whistles. It puts the wings into a position that reminds of a heart. It may jump, beat with its beak and do everything it takes to charm the female
Females are seen as much more silent and peaceful than cocks. Of course, there are always exceptions, but mostly this is the case. Females are the ones that carry the eggs and need to do the larger job, so they are the ones to be charmed: they don’t need to learn how to whistle fancy melodies. This is also why they are not as good learning words than cocks are. It’s not that they would be less intelligent – they just don’t need to. Even if the hens don’t usually sing they can still scream, squall and keep other random sounds like soft “whil-whil.” Some females actually do learn to sing but are more like something between whistling and muttering.
A female who wants to mate seems at first a bit nervous. Then she stops, lowers its back offering it for the male to step up on it, and starts to squeek silently. Hens are often wings spread, hanging upside down like bats when protecting the surroundings of their nests.
If you can’t determinate the sex of your cockatiel based on color or behavior, there is also the pelvis test. Male cockatiels have almost closed pelvis bones whereas females have more open pelvis bones. If the female has laid eggs, one could gently fit a thumb to the opening of the pelvis. This test still isn’t 100% sure. Sometimes a DNA test is needes to determinate the true gender of the cockatiel.