Animal Diversity Web

Ge­o­graphic Range

Cock­atiels are na­tive to the Aus­tralian main­land; they are widely dis­trib­uted through­out Aus­tralia, with denser pop­u­la­tions in the south­west­ern re­gion of the con­ti­nent. Cock­atiels are also found in Tas­ma­nia, but are con­sid­ered to have been in­tro­duced to this is­land ac­ci­den­tally. (Blak­ers, et al., 1984; Ka­vanau and Lee, 1987)

• Biogeographic Regions
• australian
  • native

Habi­tat

Cock­atiels are widely dis­trib­uted through the Aus­tralian main­land, tend­ing to pre­fer in­land areas to coast­lines. They tend to con­gre­gate in areas near bod­ies of fresh­wa­ter and pre­fer gen­er­ally open areas as op­posed to dense for­est. Thus, open wood­land areas en­com­passed by wa­ter­ways in ad­di­tion to sa­van­nas bor­der­ing wa­ter­holes are op­ti­mal areas to find cock­atiel flocks. Gen­er­ally no­madic, cock­atiels pre­fer Aca­cia seeds to other foods and densely pop­u­late areas with Aca­cia shrubs. (Pizzey and Knight, 1997). Cock­atiels fol­low pred­itable mi­gra­tory pat­terns in south­ern Aus­tralia, where weather pat­terns are more reg­u­lar. Here, they move in groups of one hun­dred to one thou­sand (Ka­vanau and Lee, 1987). Cock­atiels are pre­sented with large tem­per­a­ture vari­a­tions in their habi­tats, from 4.5 de­grees Cel­sius dur­ing win­ter nights to heat ex­ceed­ing 43 de­grees Cel­sius in the sum­mer (Allen and Allen, 1981). Cock­atiels are sec­ondary cav­ity nesters, pre­fer­ring large tree hol­lows when build­ing nests (typ­i­cally dead eu­ca­lypts). Nest sites are usu­ally near water, ap­prox­i­mately one to two me­ters above the ground. (Allen and Allen, 1981; Fore­shaw and Cooper, 2002; Ka­vanau and Lee, 1987; Pizzey and Knight, 1997)

• Habitat Regions
• tropical

• Terrestrial Biomes
• savanna or grassland

• Range elevation

  0 to 500 m

  0.00 to 1640.42 ft

• Average elevation

  200-500 m

  ft

Phys­i­cal De­scrip­tion

The small­est mem­ber of the Ca­ca­tu­inae sub­fam­ily (the cock­a­toos), with an av­er­age weight of 80 g, cock­atiels slen­der and stream­lined. Cock­atiels are the only type of crested par­rot that has a tail which comes to a point. This ta­pered tail is very long (ca. 15 cm), mak­ing up half of their length. In flight, these tail feath­ers spread out into a wide fan, the el­e­va­tion angle of which can be ad­justed by the bird to con­trol al­ti­tude and sta­bil­ity. While long-term ar­ti­fi­cial se­lec­tion for mu­ta­tions in color have re­sulted in many dif­fer­ent color vari­a­tions in pet cock­atiels (from the speck­led pearl mu­ta­tion to the light yel­low-white lutino mu­ta­tion), wild cock­atiels of both sexes share sim­i­lar char­ac­ter­is­tics in ap­pear­ance. Males ex­hibit dark brown to gray plumage, with patches of white bor­der­ing areas such as the upper wing when folded. Their cheeks have bright or­ange cir­cu­lar pat­terns, bor­dered by white. Fe­males are also mainly gray, with cheek patches of a drab, burnt-or­ange shade, which lack a white bor­der. Feath­ers in these cheek patches are mod­i­fied to pro­tect the ear and min­i­mize flight tur­bu­lence. The un­der­side of the tail feath­ers tends to be more com­plex in color vari­a­tion than the rest of the body, pos­sess­ing dis­tinc­tive bars of al­ter­nat­ing color. Both males and fe­males have dark brown irises and crests of ap­prox­i­mately 5 cm. These crests, com­posed of sev­eral dozen feath­ers, adorn the top of the head and are used in com­mu­ni­ca­tion; the angle at which the crest is held is in­dica­tive of a bird’s mood. Cock­atiel col­oration has re­sulted from nat­ural se­lec­tion to op­ti­mize cam­ou­flage while for­ag­ing on the ground. Their col­orations al­lows them to be eas­ily over­looked by aer­ial preda­tors, es­pe­cially in shady areas. Their beaks, char­ac­ter­is­tic of all par­rots, have curved upper sec­tions that come to a point. The nos­trils sit atop the beak at the at­tach­ment point of the upper beak to the skull and are round. The bill is dark gray, while legs are black­ish gray. Cock­atiels ex­hibit zy­go­dactyly, as do all par­rots, they have two toes fac­ing back­wards, and two fac­ing for­wards. (Allen and Allen, 1981; Blak­ers, et al., 1984; Ka­vanau and Lee, 1987; Pizzey and Knight, 1997)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes colored or patterned differently
• male more colorful

• Average mass

  80-90 g

  oz

• Average mass

  90 g

  3.17 oz

  AnAge

• Range length

  25 to 35 cm

  9.84 to 13.78 in

• Range wingspan

  40 (high) cm

  15.75 (high) in

• Average wingspan

  30-35 cm

  in

• Average basal metabolic rate

  14.2 kcal per day cm3.O2/g/hr

Re­pro­duc­tion

Cock­atiels are monog­a­mous and form re­la­tion­ships with a mate early on. These bonds serve for more than re­pro­duc­tive pur­poses - pairs stay to­gether and re­main loyal to one an­other through­out the en­tire year. Be­cause cock­atiels re­main paired through­out the year, they read­ily pro­ceed to breed­ing with­out ex­pend­ing en­ergy to find a suit­able mate. Be­fore mat­ing be­gins, there are sev­eral rit­u­al­is­tic be­hav­iors that both sexes ex­hibit. Vo­cal­iza­tion plays an im­por­tant role in com­mu­ni­cat­ing readi­ness in both sexes; fe­males emit muf­fled peeps while hold­ing their tail feath­ers erect to sig­nify readi­ness, while males are much more ag­gres­sive in their vo­cal­iza­tions, whistling unique mat­ing calls re­ferred to as songs. Males ac­com­pany these songs with a va­ri­ety of phys­i­cal be­hav­iors, in­clud­ing a strut-like walk, hold­ing of the wings erect and away from the body, and rapid beak-pound­ing to draw at­ten­tion. One of the be­hav­iors ob­served in male cock­atiels just prior to mat­ing is the ob­ser­va­tion of the nest cav­ity, a pre­s­e­lected hol­low in which to lay eggs. Males in­spect nest cav­ity for threats be­fore fe­males first enter them, and often males will re­peat­edly jump in and out of boxes to sig­nify safety. (Ka­vanau and Lee, 1987; Mar­tin and Mil­lam, 1995)

• Mating System
• monogamous
• cooperative breeder

Cock­atiel breed­ing is tied to sea­sonal changes, the most im­por­tant being rain­fall. Large spring rain­falls as­sure plen­ti­ful food sup­plies and usu­ally trig­ger mat­ing events. In­ter­est­ing field ob­ser­va­tions to note are the be­hav­iors of cock­atiels be­fore large spring rain storms: “[W]hen a thick black rain cloud dark­ens the sky, cock­atiels call ex­cit­edly to one an­other as they fly from perch to perch. The ex­cite­ment of these events usu­ally elic­its a frenzy of sex­ual dis­play by the males…who search for nest­holes ac­com­pa­nied by the hen (Smith, 1978).” As sec­ondary cav­ity nesters, cock­atiels nest in large tree hol­lows, where pairs typ­i­cally claim an en­tire tree. They pre­fer dead eu­ca­lypts ap­prox­i­mately 2 me­ters above the ground and close to a source of fresh­wa­ter; these snags rid­dled with cracks are fa­vored as they are less likely to be­come flooded with water dur­ing pe­ri­ods of ex­cess rain­fall. Upon ob­tain­ing an ad­e­quate nest hole and after safety in­spec­tions by the male, mat­ing can com­mence. Once stored in the oviduct, cock­atiel sper­ma­to­zoa are long-lived, al­low­ing egg fer­til­iza­tion up to a month after dis­po­si­tion. Fe­males oviposit as soon as four days after find­ing a nest hole, and clutch sizes gen­er­ally av­er­age from four to seven eggs, which are laid every other day. Fe­male cock­atiels are in­de­ter­mi­nate egg-lay­ers, hav­ing the abil­ity to re­place lost or bro­ken eggs with more. Hence, if nu­tri­tional de­mands are sus­tained, fe­males can con­tinue to lay eggs until a clutch of ap­pro­pri­ate size is es­tab­lished. Eggs are in­cu­bated for 17 to 23 days and chicks are in­de­pen­dent and leave the nest by five weeks, though sex­ual ma­tu­rity is not reached until 13 months in males and 18 months in fe­males. (Ka­vanau and Lee, 1987; Mil­lam, et al., 1996; Smith, 1978; Spoon and Mil­liam, 2006)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
• oviparous

• Breeding interval

  Cockatiels breed once yearly with their mates, usually triggered by rainfall.

• Breeding season

  Breeding typically occurs from August to December.

• Range eggs per season

  4 to 7

• Average eggs per season

  5

• Range time to hatching

  17 to 23 days

• Range fledging age

  3 to 5 weeks

• Average time to independence

  4-5 weeks

• Average age at sexual or reproductive maturity (female)

  18 months

• Average age at sexual or reproductive maturity (male)

  13 months

Cock­atiels have a strong parental drive and both par­ents share re­spon­si­bil­i­ties in the hatch­ing and rais­ing of chicks. Both male and fe­male chicks have unique roles in in­cu­bat­ing eggs; males in­cu­bate eggs from early morn­ing to late af­ter­noon, while fe­males in­cu­bate through­out the en­tire night. Males stand out­side the nest cav­ity near the en­trance at night­fall. When chicks hatch, both par­ents par­tic­i­pate in allofeed­ing, the process through which food is passed from one bird to an­other, but the male mainly car­ries this role. This feed­ing process is usu­ally ini­ti­ated 2 h post-hatch. Cock­atiels rarely aban­don chicks; in cap­tive stud­ies many would not leave the nest box un­less phys­i­cally re­moved by re­searchers. As many du­ties are shared by both par­ents, parental com­pat­i­bil­ity is es­sen­tial in cock­atiels; a study by Spoon and Mil­liam (2006) sug­gests that this com­pat­i­bil­ity cor­re­lates to many as­pects of re­pro­duc­tive suc­cess, in­clud­ing clutch size and num­ber of chicks raised to in­de­pen­dence. (Ka­vanau and Lee, 1987; Mar­tin and Mil­lam, 1995; Mil­lam, et al., 1996; Spoon and Mil­liam, 2006)

• Parental Investment
• altricial
• male parental care
• female parental care
• pre-fertilization
  • provisioning
  • protecting
    • male
    • female
• pre-hatching/birth
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
  • protecting
    • female
• pre-independence
  • provisioning
    • male
  • protecting
    • male
    • female

Lifes­pan/Longevity

Wild cock­atiels have a lifes­pan of 10 to 14 years. Those in cap­tiv­ity can live much longer; ex­ten­sive re­search in cock­atiel nu­tri­tion and meta­bolic re­quire­ments have al­lowed for diet op­ti­miza­tion to achieve op­ti­mum health. Cap­tive cock­atiels can live for up to 25 years, with the old­est on record reach­ing an in­cred­i­ble 36 years old. Diet and en­vi­ron­men­tal fac­tors play es­sen­tial roles in cock­atiel lifes­pan. (Ka­vanau and Lee, 1987; Mc­Caf­fery, 2009)

• Range lifespan
  Status: captivity

  36 (high) years

• Average lifespan
  Status: wild

  10-14 years

• Average lifespan
  Status: captivity

  15-25 years

• Average lifespan
  Status: captivity

  35 years

  AnAge

Be­hav­ior

Cock­atiels are ex­cep­tion­ally so­cial birds, es­tab­lish­ing pair bonds early on and usu­ally feed­ing and mov­ing to­gether in groups of sev­eral birds to larger flocks of up to sev­eral thou­sand. Mi­gra­tory pat­terns are re­gion-spe­cific; north­ern Aus­tralia’s wet­ter cli­mates have more no­madic cock­atiel pop­u­la­tions, con­tin­u­ally re­lo­cat­ing to fresh water and food, while the weather pat­terns of south­ern Aus­tralia offer more pre­dictabil­ity, thus south­ern cock­atiels sea­son­ally mi­grate in groups. Cock­atiels are timid by na­ture and ex­hibit sev­eral pref­er­ences in nest­ing habits, for­ag­ing habits, and more. With no preva­lent nat­ural de­fense mech­a­nisms, cock­atiels al­ways choose flight when a threat is per­ceived; they are able to at­tain speeds in ex­cess of 40 miles per hour in the air. Cock­atiel feath­ers serve many im­por­tant phys­i­o­log­i­cal pur­poses and often feather pre­sen­ta­tion in cock­atiels is in­dica­tive of mood; cock­atiels con­tract feath­ers to ap­pear very thin when fright­ened, and puff them out when con­tent. Feath­ers serve as the means through which flight is achieved, but also pro­vide in­su­la­tion to con­serve body heat; cock­atiels must main­tain in­ter­nal body tem­per­a­tures in ex­cess of 100 de­grees Fahren­heit (38 de­grees Cel­sius). Outer feath­ers are wa­ter­proofed. This is achieved through preen­ing, which can con­sti­tute a sub­stan­tial por­tion of a cock­tiel’s daily rou­tine. Cock­atiels wa­ter­proof their outer feath­ers by mak­ing di­rect beak con­tact with their uropy­gials or se­ba­ceous glands, which se­crete an oily sub­stance that they then man­u­ally coat their feath­ers with. Sim­i­lar to other mem­bers of the Ca­ca­tu­inae sub­fam­ily, cock­atiels have a pow­der down com­posed of ker­atin. This pow­der down serves to fur­ther wa­ter­proof feath­ers, but is re­moved in ex­cess through preen­ing. Large clouds of dust can be seen com­ing from perch­ing cock­atiels as they shake them­selves after a preen­ing ses­sion. A final im­por­tant as­pect of preen­ing comes in the con­tents of oil se­creted from the uropy­gial. This oil con­tains vi­t­a­min D pre­cur­sors that coat feath­ers; these pre­cur­sors when ex­posed to sun­light ac­ti­vate to pro­duce vi­t­a­min D, which is es­sen­tial for cal­cium ab­sorp­tion. Cock­atiels in­gest this syn­the­sized vi­t­a­min D while preen­ing. (Blak­ers, et al., 1984; Cay­ley, 1931; Ka­vanau and Lee, 1987; Mc­Caf­fery, 2009)

• Key Behaviors
• arboreal
• scansorial
• flies
• diurnal
• motile
• nomadic
• migratory
• social

• Average territory size

  4.8 km^2

Home Range

Cock­atiel ter­ri­to­ries can span sev­eral miles from their nest. As they gen­er­ally nest close to an avail­able fresh­wa­ter source, they don’t typ­i­cally have to travel far to hy­drate them­selves. How­ever, groups of cock­atiels can ven­ture great dis­tances from their nests dur­ing nor­mal for­ag­ing on the ground for seeds. These dis­tances can be achieved rel­a­tively quickly, thanks to their high flight speeds. (Ka­vanau and Lee, 1987)

Com­mu­ni­ca­tion and Per­cep­tion

Cock­atiels are un­like some larger species of par­rots in that they can­not ac­cu­rately im­i­tate the human voice, but have the abil­ity to mimic melodies and can sing. Cock­atiels have a range of dis­tinc­tive vari­a­tions used to com­mu­ni­cate moods. High-pitched chirps can be in­dica­tive of stress and, by the pitch and du­ra­tion of the cry, the mag­ni­tude of the stres­sor can in some cases be de­ter­mined. For ex­am­ple, cries of a lower pitch can be in­dica­tive of a mild stres­sor, while higher pitched cries are ac­com­pa­nied by flight. This in­di­cates that a threat is se­vere enough to cause im­me­di­ate eva­sion. Cock­atiels can com­mu­ni­cate over rel­a­tively large dis­tances, as they are shrill and very loud. Other forms of vocal com­mu­ni­ca­tion are male songs, which are pro­longed calls oc­cur­ring dur­ing mat­ing pe­ri­ods to in­di­cate avail­abil­ity and at­tract fe­males. Cock­atiels also ex­press mood vi­su­ally through the use of their crests. The crest is held ver­ti­cally erect when the bird is star­tled or is alert. When con­tent, it is gen­er­ally held at roughly a 45-de­gree angle to the head. When ag­i­tated or threat­ened, the crest is held flat against the head. Dur­ing flight, the crest is also laid flat against the skull, re­duc­ing wind drag. An­other no­table be­hav­ior is the spread­ing of the wings both up­wards and out­wards while at rest. This is typ­i­cally seen in re­pro­duc­tive courtships by both sexes and is often used as a vi­sual method to im­press an­other bird. (Blak­ers, et al., 1984; Ka­vanau and Lee, 1987; Pizzey and Knight, 1997)

• Communication Channels
• visual

• Other Communication Modes
• mimicry

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Cock­atiels are al­most ex­clu­sively ground for­agers. They are zy­go­dacty­lous, their long toes not only serve to wrap around perches, but also ex­tend out­ward to make ex­tremely large, sta­ble feet for walk­ing on the ground. While cock­atiels can feed on a va­ri­ety of plant and an­i­mal mat­ter, their sharp curved beaks are adapted to max­i­mize ef­fi­ciency in shuck­ing and con­sum­ing seeds, their food of choice. Ei­ther in pairs, small groups of 6 to 8 birds, or larger flocks of sev­eral hun­dred birds, cock­atiels search open areas for sun-dried seeds from grasses, shrubs, and trees. Cock­atiels use their tongues to ro­tate seeds as they use their upper beak to re­move shells; they can re­move a shell and con­sume a seed in only a few sec­onds. Cock­atiels also re­move seeds di­rectly from branches. Cock­atiels ob­tain water pri­mar­ily from fresh­wa­ter pools such as wa­ter-holes. Vul­ner­a­ble to pre­da­tion on the ground, they drink rapidly, usu­ally only tak­ing one to two sips of water, then ex­tend­ing their necks up­wards to swal­low and sur­vey their sur­round­ings. Cock­atiels uti­lize meta­bolic water pro­duc­tion, and can go for long amounts of time with­out drink­ing. Ver­sa­tile in their feed­ing be­hav­ior, cock­atiels can also con­sume softer foods, such as fruits and berries. They have also been ob­served to eat small ground-dwelling in­sects. Cock­atiels re­main silent dur­ing for­ag­ing. (Blak­ers, et al., 1984; Ka­vanau and Lee, 1987)

• Primary Diet
• herbivore
  • granivore

• Animal Foods
• insects

• Plant Foods
• seeds, grains, and nuts
• fruit

Pre­da­tion

Aus­tralian birds of prey are the pri­mary preda­tors of cock­atiels. Cock­atiels are mostly preyed upon from above while feed­ing by rap­tors. They are cam­ou­flaged to blend in with the ground. Other than their col­oration, cock­atiels have no nat­ural de­fenses to preda­tors other than their high-speed flight. Thus, cock­atiels al­ways re­spond to threats by aer­ial eva­sion. They also use loud, shrill vo­cal­iza­tions to com­mu­ni­cate threats among each other and stay in large flocks, where many eyes can look for preda­tors. Cock­atiels can also in ex­treme cir­cum­stances de­liver a pow­er­ful bite from their sharp beaks and well-de­vel­oped jaw mus­cles, which can eas­ily pierce the skin. Cock­atiels bite as a last re­sort de­fense mech­a­nism, which can be ob­served in nest­ing cock­atiels con­fronted with an in­va­sive preda­tor to the nest­box. (Ka­vanau and Lee, 1987)

• Anti-predator Adaptations
• aposematic
• cryptic

• Known Predators

  • raptors (Falconiformes)

Ecosys­tem Roles

Al­though they pre­fer sun-dried seeds, cock­atiels can serve the role of seed-dis­persers in their ecosys­tems when they choose to con­sume fresh seeds, as they are very messy eaters and scat­ter seeds and shells as far as four to five feet away from them­selves when they eat. They can also dis­perse the seeds of the fruits they con­sume.

Cock­atiels are also sus­cep­ti­ble to bac­te­r­ial in­fec­tion, par­tic­u­larly in the liver, and in such cases har­bor bac­te­ria such as Gi­a­r­dia lam­blia and Cryp­tosporid­ium galli, which are as­so­ci­ated with weight loss, ab­nor­mal drop­pings, and mor­tal­ity. (An­tunes, et al., 2008)

• Ecosystem Impact
• disperses seeds

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Cock­atiels are pop­u­lar pets, the sec­ond most pop­u­lar bird after budgeri­gars. Through se­lec­tive breed­ing, dozens of color mu­ta­tions have been achieved; per­haps the most ex­treme of these is the lutino vari­a­tion, in which the cock­atiel is com­pletely white or light yel­low, with only its bright or­ange cheek patches ac­cen­tu­at­ing this uni­form color. Cock­atiels bred se­lec­tively can sell for high prices. So­ci­eties such as the Na­tional Cock­atiel So­ci­ety host reg­u­lar shows and ex­hi­bi­tions in which cock­atiel breed­ers can show­case their birds and com­pete for prizes. Many stu­dents also ben­e­fit from cock­atiels by con­duct­ing re­search in uni­ver­sity set­tings. The Psittacine Re­search Group in Cal­i­for­nia is one group that has an es­tab­lished cock­atiel colony de­voted to re­search. This lab­o­ra­tory has pro­vided stu­dents with re­search ex­pe­ri­ence, as well as valu­able data to the sci­en­tific com­mu­nity con­cern­ing cock­atiel nu­tri­tion and be­hav­ior. (Ka­vanau and Lee, 1987; Mc­Caf­fery, 2009; Roudy­bush and Grau, 1991)

• Positive Impacts
• pet trade
• research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Cock­atiels can be re­garded as pests to agri­cul­tural in­dus­tries in Aus­tralia, where flocks of sev­eral thou­sand have been known to raid crop fields, par­tic­u­larly fields of sorghum, mil­let, wheat, and sun­flow­ers. There have been open sea­sons on cock­atiels in Queens­land, Aus­tralia. They are gen­er­ally pro­tected by law and are some­times dealt with by the use of pes­ti­cides to deter them from fields. (Ka­vanau and Lee, 1987)

• Negative Impacts
• crop pest

Con­ser­va­tion Sta­tus

Cock­atiels have a very large range and densely pop­u­late the Aus­tralian main­land. The exact pop­u­la­tion has never been quan­ti­fied for this rea­son and they are not con­sid­ered threat­ened cur­rently.

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  No special status

• US Federal List

  No special status

• CITES

  Appendix II

• State of Michigan List

  No special status

Other Com­ments

As pets, cock­atiels are ex­tremely loyal to their own­ers once they have es­tab­lished a bond, which is sim­i­lar to the pair-bonds be­tween wild cock­atiels. Cock­atiels are also fa­vored to other birds par­tially be­cause of their so­cial rit­u­als with one an­other in the wild; pair bonds show af­fec­tion by groom­ing each other’s head, so pet cock­atiels enjoy being stroked on the head, often low­er­ing their heads to sig­nify their de­sire to be pet­ted. Male cock­atiels can also mimic melodies, fur­ther in­creas­ing their pop­u­lar­ity. (Allen and Allen, 1981)

Con­trib­u­tors

Bran­don Newmyer (au­thor), Rad­ford Uni­ver­sity, Karen Pow­ers (ed­i­tor), Rad­ford Uni­ver­sity, Tanya Dewey (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Allen, G., C. Allen. 1981. Cock­atiel Hand­book. Nep­tune, New Jer­sey: TFH Pub­lish­ing Co.

An­tunes, R., D. Simoes, A. Naka­mura, M. Meire­les. 2008. Nat­ural in­fec­tion with Cryp­tosporid­ium galli in Ca­naries (Ser­i­nus ca­naria), in a Cock­atiel (Nymph­i­cus hol­landi­cus) and in Lesser Seed-Finches (Ory­zoborus an­golen­sis) from Brazil. Avian Dis­eases, 52: 702-705.

Blak­ers, M., S. Davies, P. Reilly. 1984. The Atlas of Aus­tralian Birds. Beaver­ton, OH: Mel­bourn Uni­ver­sity Press.

Cay­ley, N. 1931. What bird is that? A guide to the birds of Aus­tralia.. Syd­ney, Aus­tralia: Angus and Robert­son LTD.

Fore­shaw, J., W. Cooper. 2002. Aus­tralian Par­rots 3rd edi­tion. Mel­bourne, Lans­downe: Avi-Trader Pub­lish­ing.

Ka­vanau, , Lee. 1987. Be­hav­ior and evo­lu­tion: love­birds, cock­atiels, and budgeri­gars.. Los An­ge­les, Cal­i­for­nia: Sci­ence Soft­ware Sys­tems.

Mar­tin, S., R. Mil­lam. 1995. Nest box se­lec­tion by floor lay­ing and re­pro­duc­tively naive cap­tive cock­atiels. Ap­plied An­i­mal Sci­ence, 43: 95-109.

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