The Cockatiel (Nymphicus hollandicus), also known as the Quarrion and the Weero, is a diminutive cockatoo endemic to Australia and prized as a household pet. They are relatively easy to breed and keep in captivity and they are kept throughout the world as pets.
The only member of the genus Nymphicus, the Cockatiel has previously been considered a crested parrot or small cockatoo. However, more recent molecular studies have settled the debate, showing their closest relatives to be the black cockatoos of the genus Calyptorhynchus. They are hence now classified as the smallest of the Cacatuidae (cockatoo family). Cockatiels are natively found across the outback regions of inland Australia, and favour the Australian wetlands, scrublands, and bush lands.

The Cockatiel's distinctive erectile crest expresses the animal's state of being. (Some say "emotional state.") The crest is dramatically vertical when the cockatiel is startled or excited, gently oblique in its neutral or relaxed state, and flattened close to the head when the animal is angry or defensive. The crest is also held flat but protrudes outward in the back when the cockatiel is trying to appear alluring or flirtatious.

Description
In contrast to most Cockatoos, the Cockatiel has long tail feathers roughly making up half of its total length. At 300 mm to 330 mm (12 to 13 ins), the Cockatiel is the smallest and only parakeet type of Cockatoo species. The latter ranging between 300 mm to 600 mm (12-24 in) in length.

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 colouration is generally vibrant in adult males, and often quite muted in females. Visual sexing is often possible with this variant of the bird.

Distribution and Habitat
Cockatiels are native only to Australia where they are found largely in arid or semi-arid country, but always near water. Sometimes hundreds will flock around a single such body of water. To farmers' dismay, they often eat cultivated crops. They are absent from the most fertile southwest and southeast corners of the country, the deepest Western Australian deserts, and Cape York Peninsula. They are the only Cockatoo species which can sometimes reproduce in the end of their first year.

Lifespan
The Cockatiel's lifespan in captivity is generally given as 15-20 years, though it is sometimes given as short as 10-15 years, and there are reports of Cockatiels living as long as 30 years, the oldest confirmed specimen reported being 35 years old when it died. A cockatiel lived to be 27 years old in Manchester, UK. Diet and exercise, much like in humans, are often major determining factors in cockatiel lifespan.

Aviculture
Cockatiels are generally regarded as good pets having a "sweet" demeanor, though this is by no means a guarantee. Like most other pets, the manner in which the animal is raised, handled, and kept has a profound effect on the temperament of the animal. Some birds are quite gregarious and sociable while others can be shy, retreating to the back of the cage when an unfamiliar figure appears.
Generally, well-socialised birds are gentle and friendly. Some cockatiels enjoy physical contact, lending themselves well to taming. Many cockatiel owners develop regular bonding rituals with their animals, engaging in preening, scratching, and even petting. Cockatiels which are hand-fed and purchased from a young age are more readily suited for physical contact.
Some birds will emit a distinctive "hiss" when irritated, retreating rapidly or defending with pecking bites, which can be relatively strong for their size. This "hiss" is a form of mimicry used in a defensive attempt to confuse the cockatiel's most common predator, the snake.
Cockatiels do have a reputation for being quite noisy and demanding of the attention of their owners on a regular basis. Their vocalisations range from ginger cheeps to piercing cries.
They can be made more secure (in the mood for singing/mimicry, playing, etc) when they have a consistent few hours of quality time per day with a person or in a person's company and a good night's sleep. Twelve hours of sleep at least is required for a happy pet, sleep taken away can cause sickness and grumpy pets. If left of their own, quiet birds will frequently make contact calls with their owners, calls that sometimes can be quite loud if the person is out of sight. Cockatiels can grow so attached to their owners that they may try to 'protect' them from anyone that tries to come near them, such as a partner or family member, by biting or hissing. This happens especially if cockatiels are kept in bedrooms or other rooms that are not generally shared by everyone in the family, because cockatiels perceive those rooms as their own personal territory. By keeping cockatiels in a shared household room, they are exposed to all family members equally and will not favour one person and feel the need to defend him or her as much. Cockatiels must be acquainted with the entire family, in order to assure even temperament toward all. A scared cockatiel will choose flight over fight most of the time, thus creating a chance for injury (i.e. flying into a glass door). Their popularity as pets is in part because of their calm and timid temperament, to the point that they can even be bullied by smaller but more confident birds such as Budgerigars[]. Budgerigars and other smaller birds may choose to pick at cockatiels' feet causing lost toes. It is not uncommon at all for a larger or smaller bird to maim the cockatiel, creating life-long disabilities and potentially life threatening injuries. However, some cockatiels will defend themselves.
Once bonded with their owners, they will often cuddle and play, pushing their head against hands or faces, and may nibble at fingers for attention to get a scratch on the head and neck.Cockatiels, like almost all other parrots, love to chew paper and can destroy objects (like cardboard, books, magazines, wicker baskets, etc) left unattended. Most cockatiels enjoy looking at themselves in mirrors and will engage in the activity for hours. Cockatiels that are exposed to mirrors perceive their reflections as their mates. This can induce very aggressive behaviour, and upon seeing themselves once, they are likely to experience anxiety until they find the mirror again.
The Cockatiel, along with the Budgerigar, is among the most popular pet bird species. Today all Cockatiels available in the pet trade are captive-bred, as Australia no longer permits the export of native wildlife, whether endangered or not

Vocalisation
Although cockatiels are part of the parrot order, they are better at imitating whistles than speech. Although they can learn words, the only understandable parts of the words are the inflections, while the consonants are not easily discernible. Their whistles and other mimicking sounds such as 'lip-smacking' and 'tutting' are almost perfect imitations of the sounds their owners make. Although some cockatiels do learn to repeat phrases, males are generally better at mimicry than females.[ Cockatiel speech often comes out as a "whistle" when they do annunciate, the voice being soft in volume and difficult to make out. Cockatiels can mimic many sounds, such as the bleep of a car alarm, a ringing telephone, the sound of a zipper, the beeping of cell phones or microwaves, or the calls of other bird species such as blue jays or chickadees and loud weather like thunder. They can also mimic other pets such as dogs, occasionally barking back.
Although some say that female cockatiels cannot speak, this is not an absolute. Males have been known to mimic noises, words and sometimes other animals. Females generally don't imitate speech, but tend to mimic sounds such as telephones, washing machines, toilet flushes, etc. Cockatiels that do imitate speech will usually mimic frequently heard phrases, particularly of the individual to whom the bird feels closest.