Cockatiels, Nymphicus Hollandicus, are the smallest cousin of the cockatoo. Cockatiels are very popular as pets for good reason. They have a big personality for their relatively small size and they are very intelligent. They can be taught to talk and do some simple tricks, and many can whistle complete songs. Some have been known to have a large vocabulary, but they can't rival the larger parrots in this area. Males tend to be more vocal than females and learn to speak and whistle more quickly. But all my females can at least do the wolf whistle. They are by no means incapable.  

Cockatiels as a whole are known to have a sweet and inquisitive demeanor. Adult birds that have not been handled much may prove to be extremely hard to tame, but a young hand raised bird can quickly become a beloved member of the family. Most enjoy being scratched and petted and would be perfectly content to sit on your shoulder for hours while you do your normal routine around the house.

The average lifespan of the cockatiel is 15-20 years although diet and exercise can have a huge impact on this. The oldest recorded cockatiel was 35 years old when it died. If you are considering a cockatiel as a pet be aware that this will be a long commitment.

The minimum cage size for a cockatiel should be AT LEAST 30"x18"x18" for one bird. This will give him plenty of room to stretch his wings and move around. Bar spacing should be 1/2" so they can't get their heads between them and end up stuck. The perches should be between 1/2" and 1 1/2". A bird's feet should not be able to wrap around the perch completely or even nearly so. Choosing a perch that has a lot of variation in thickness rather than a smooth one is a good idea to keep the feet exercised and strong.

A mixed seed cockatiel diet is ok, but I recommend a fortified pellet food with the daily addition of millet and fresh fruit. A pelleted food makes it impossible for your bird to sift through and consume only his favorites and thus ensures a balanced diet. Clean water should be available at all times. It may be wise to train your bird to drink from a bottle instead of a bowl. This will keep him from soiling it or flinging food in it.

The "Normal Grey" or "Wild-type" cockatiel's plumage is primarily grey with prominent white flashes on the outer edges of each wing. The face of the male is yellow or white, while the face of the female is primarily grey or light grey, and both genders feature a round orange area on both ear areas, often referred to as "cheek patches." This orange coloration is generally vibrant in adult males, and often quite muted in females.
 
These days there are a number of mutations that are recognized by the National Cockatiel society and other organizations. To go into any detail about this would take a great amount of time. Cinnamons, lutinos, fallows, yellowcheeks, whiteface, pearls, pieds and multiple combinations of the above are just a few examples. Many of these cannot be visually sexed like the original gray.