Editing Kākāpō (section)

==Description==
[[File:Strigops habroptilus 1-1c.jpg|thumb|A year-old kākāpō on [[Codfish Island / Whenua Hou]].]]
The kākāpō is a large, rotund parrot. Adults can measure from {{cvt|58|to|64|cm}} in length with a wingspan of {{cvt|82|cm}}. Males are significantly heavier than females with an average weight of {{cvt|2|kg}} compared with just {{cvt|1.5|kg}} for females.{{sfn|Higgins|1999|p=633}} Kākāpō are the heaviest living species of parrot and on average weigh about {{cvt|400|g|oz}} more than the largest flying parrot, the [[hyacinth macaw]].<ref name=hbw>{{ cite book | last=Collar | first=N.J. | year=1997 | chapter=Family Psittarcidae (Parrots) | editor1-last=del Hoyo | editor1-first=J. | editor2-last=Elliott | editor2-first=A. | editor3-last=Sargatal | editor3-first=J. | title=Handbook of the Birds of the World | volume=4: Sandgrouse to Cuckoos | location=Barcelona, Spain | publisher=Lynx Edicions | isbn=978-84-87334-22-1 | pages=280–479 [287, 419] | chapter-url=https://archive.org/details/handbookofbirdso0004unse/page/287/mode/1up | chapter-url-access=registration }}</ref>

The kākāpō cannot fly, having relatively short wings for its size and lacking the [[Keel (bird anatomy)|keel]] on the [[sternum]] (breastbone), where the flight muscles of other birds attach.<ref name="Powlesland2006" /> It uses its wings for balance and to break its fall when leaping from trees. Unlike many other land birds, the kākāpō can accumulate large amounts of body fat.<ref name="Powlesland2006"/>

The upper parts of the kākāpō have yellowish moss-green feathers barred or mottled with black or dark brownish grey, blending well with native vegetation. Individuals may have strongly varying degrees of mottling and colour tone and intensity – museum specimens show that some birds had completely yellow colouring. The breast and flank are yellowish-green streaked with yellow. The belly, undertail, neck, and face are predominantly yellowish streaked with pale green and weakly mottled with brownish-grey. Because the feathers do not need the strength and stiffness required for flight, they are exceptionally soft, giving rise to the [[specific name (zoology)|specific epithet]] ''habroptila''. The kākāpō has a conspicuous facial disc of fine feathers resembling the face of an owl; thus, early European settlers called it the "owl parrot". The beak is surrounded by delicate feathers which resemble [[whiskers|vibrissae]] or "whiskers"; it is possible kākāpō use these to sense the ground as they walk with its head lowered, but there is no evidence for this. The mandible is variable in colour, mostly ivory, with the upper part often bluish-grey. The eyes are dark brown. Kākāpō feet are large, scaly, and, as in all parrots, [[dactyly|zygodactyl]] (two toes face forward and two backward). The pronounced claws are particularly useful for climbing. The ends of the tail feathers often become worn from being continually dragged on the ground.<ref name="Powlesland2006"/>

[[File:Kākāpō head.jpg|thumb|left|The "whiskers" around the beak]]

Females are easily distinguished from males as they have a narrower and less domed head, narrower and proportionally longer beak, smaller [[Beak#Cere|cere]] and [[Beak#Nares|nostrils]], more slender and pinkish grey legs and feet, and proportionally longer tail. While their plumage colour is not very different from that of the male, the toning is more subtle, with less yellow and mottling. Nesting females also have a [[brood patch]] of bare skin on the belly.<ref name="Powlesland2006"/>

The kākāpō's [[Altriciality|altricial]] young are first covered with greyish white down, through which their pink skin can be easily seen. They become fully feathered at approximately 70 days old. Juvenile individuals tend to have duller green colouration, more uniform black barring, and less yellow present in their feathers. They are additionally distinguishable because of their shorter tails, wings, and beaks. At this stage, they have a ring of short feathers surrounding their irises that resembles eyelashes.<ref name="Powlesland2006" />

Like many other parrots, kākāpō have a variety of calls. As well as the ''booms'' (see [[#Breeding|below]] for a recording) and ''chings'' of their mating calls, they will often loudly ''skraark''.<ref name="CloseUp"/>

The kākāpō has a well-developed [[Olfaction|sense of smell]], which complements its nocturnal lifestyle.<ref name="Hagelin04">{{Cite journal |last1=Hagelin |first1=Julie C. |doi=10.1111/j.1474-919X.2004.00212.x |title=Observations on the olfactory ability of the kakapo ''Strigops habroptilus'', the critically endangered parrot of New Zealand |journal=[[Ibis (journal)|Ibis]] |volume=146 |issue=1 |pages=161–164 |date=2004}}</ref> It can distinguish between odours while foraging, a behaviour reported in only one other parrot species.<ref name="Hagelin04"/> The kākāpō has a large olfactory bulb ratio (longest diameter of the olfactory bulb/longest diameter of the brain) indicating that it does, indeed, have a more developed sense of smell than other parrots.<ref name="Hagelin04" /> One of the most striking characteristics of the kākāpō is its distinct musty-sweet odour.<ref name="CloseUp">{{cite web|url=http://kakaporecovery.org.nz/up-close-and-personal/|title=Up Close & Personal|publisher=Kakapo Recovery|access-date=5 March 2014}}</ref> The smell often alerts predators to the presence of kākāpō.<ref>{{cite web|url=http://www.wildinfo.net/facts/Kakapo.asp?page=/facts/Kakapo.asp|title=Kakapo (''Strigops habroptilus'')|publisher=Wild Magazine}}</ref>

As a nocturnal species, the kākāpō has adapted its senses to living in darkness. Its [[optic tectum]], nucleus rotundus, and [[Avian pallium|entopallium]] are smaller in relation to its overall brain size than those of diurnal parrots. Its retina shares some qualities with that of other nocturnal birds but also has some qualities typical of diurnal birds, lending to best function around twilight. These modifications allow the kākāpō to have enhanced light sensitivity but with poor visual acuity.<ref>{{cite journal |last1=Corfield |first1=J. R. |last2=Gsell |first2=A. C. |last3=Brunton |first3=D. |last4=Heesy |first4=C. P. |last5=Hall |first5=M. I. |last6=Acosta |first6=M. L. |last7=Iwaniuk |first7=A. N. |year=2011 |title=Anatomical specializations for nocturnality in a critically endangered parrot, the kakapo (''Strigops habroptilus'') |journal=PLOS ONE |volume=6 |issue=8 |page=e22945 |doi=10.1371/journal.pone.0022945 |pmid=21860663 |pmc=3157909 |bibcode=2011PLoSO...622945C |doi-access=free}}</ref>

===Internal anatomy===
[[File:Strigops habroptilus (AM LB299).jpg|thumb|upright|Skeleton]] 
The skeleton of the kākāpō differs from other parrots in several features associated with flightlessness. Firstly, it has the smallest relative wing size of any parrot. Its wing feathers are shorter, more rounded, less asymmetrical, and have fewer distal barbules to lock the feathers together. The sternum is small and has a low, [[vestigial]] keel and a shortened spina externa. As in other flightless birds and some flighted parrots, the [[furcula]] is not fused but consists of a pair of [[clavicles]] lying in contact with each [[coracoid]]. As in other flightless birds, the angle between the coracoid and sternum is enlarged. The kākāpō has a larger pelvis than other parrots. The proximal bones of the leg and wing are disproportionately long and the distal elements are disproportionately short.<ref name="Livezey1992">{{Cite journal |last1=Livezey |first1=Bradley C. |doi=10.1002/jmor.1052130108 |pmid=29865598 |title=Morphological corollaries and ecological implications of flightlessness in the kakapo (Psittaciformes: ''Strigops habroptilus'') |journal=Journal of Morphology |volume=213 |issue=1 |pages=105–145 |date=1992 |s2cid=206090256}}</ref>

The [[pectoralis major muscle|pectoral]] musculature of the kākāpō is also modified by flightlessness. The pectoralis and [[supracoracoideus]] muscles are greatly reduced. The propatagialis tendo longus has no distinct muscle belly. The sternocoracoideus is tendinous. There is an extensive cucularis capitis clavicularis muscle that is associated with the large [[crop (anatomy)|crop]].<ref name="Livezey1992"/>

===Genetics===
Because kākāpō passed through a [[Population bottleneck|genetic bottleneck]], in which their world population was reduced to 49 birds, they are extremely inbred and have low genetic diversity. This manifests in lower disease resistance and in fertility problems: 61% of kākāpō eggs fail to hatch.<ref>{{Cite journal |last1=Savage |first1=J.L. |last2=Crane |first2=M.S. |last3=Hemmings |first3=N. |date=2021 |title=Low hatching success in the critically endangered kākāpō is driven by early embryo mortality not infertility |journal=Animal Conservation |volume=25 |issue=3 |pages=352–360 |doi=10.1111/acv.12746|s2cid=244579763 |doi-access=free }}</ref><!--

See https://zslpublications.onlinelibrary.wiley.com/doi/full/10.1111/acv.12746

--> Beginning in 2015, the Kākāpō 125+ project has sequenced the [[genome]] of all living kākāpō, as well as some museum specimens.<ref>{{Cite web |first= |date=2023 |title=Kākāpō gene sequencing |url=https://www.doc.govt.nz/our-work/kakapo-recovery/what-we-do/research-for-the-future/kakapo125-gene-sequencing/ |website=Department of Conservation, New Zealand Government}}</ref> The project is a collaboration led by Genomics Aotearoa and a collaboration with a team of international collaborators.<ref name="White20160">{{Cite journal |last=White |first=Rebekah |date=Sep–Oct 2016 |title=Decoding Kākāpō |url=https://www.nzgeo.com/stories/decoding-kakapo/ |journal=New Zealand Geographic |volume=141}}</ref><ref>{{Cite web |first= |date=2023 |title=Kākāpō125+ gene sequencing |url=https://www.doc.govt.nz/our-work/kakapo-recovery/what-we-do/research-for-the-future/kakapo125-gene-sequencing/ |website=Department of Conservation, New Zealand Government}}</ref>

A [[DNA sequencing|DNA sequence analysis]] was performed on 35 kākāpō genomes of the surviving descendants of an isolated island population, and on 14 genomes, mainly from museum specimens, of the now extinct mainland population.<ref name = Dussex2021>{{Cite journal | last1=Dussex | first1=N. | last2=van der Valk | first2=T. | last3=Morales | first3=H.E. | last4=Wheat | first4=C.W. | last5=Díez-del-Molino | first5=D. | last6=von Seth | first6=J. | last7=Foster | first7=Y. | last8=Kutschera | first8=V.E. | last9=Guschanski | first9=K. | last10=Rhie | first10=A. | last11=Phillippy | first11=A.M. | last12=Korlach | first12=J. | last13=Howe | first13=K. | last14=Chow | first14=W. | last15=Pelan | first15=S. | last16=Mendes Damas | first16=J.D. | last17=Lewin | first17=H.A. | last18=Hastie | first18=A.R. | last19=Formenti | first19=G. | last20=Fedrigo | first20=O. | last21=Guhlin | first21=J. | last22=Harrop | first22=T.W.R. | last23=Le Lec | first23=M.F. | last24=Dearden | first24=P.K. | last25=Haggerty | first25=L. | last26=Martin | first26=F.J. | last27=Kodali | first27=V. | last28=Thibaud-Nissen | first28=F. | last29=Iorns | first29=D. | last30=Knapp | first30=M. | last31=Gemmell | first31=N.J. | last32=Robertson | first32=F. | last33=Moorhouse | first33=R. | last34=Digby | first34=A. | last35=Eason | first35=D. | last36=Vercoe | first36=D. | last37=Howard | first37=J. | last38=Jarvis | first38=E.D. | last39=Robertson | first39=B.C. | last40=Dalén | first40=L. | date=2021 | title=Population genomics of the critically endangered kākāpō | journal=Cell Genomics | volume=1 | issue=1 | pages=100002 | doi=10.1016/j.xgen.2021.100002 | pmid=36777713 | pmc=9903828 | doi-access=free }}</ref> An analysis of the long-term genetic impact of small population size indicated that the small island kākāpō population had a reduced number of harmful [[mutation]]s compared to the number in mainland individuals.<ref name = Dussex2021/>  It was hypothesized that the reduced mutational load of the island population was due to a combination of [[genetic drift]] and the purging of deleterious mutations through increased [[inbreeding]] and [[Negative selection (natural selection)|purifying selection]] that occurred since the isolation of this population from the mainland about 10,000 years ago.<ref name = Dussex2021/>  Purging of deleterious mutations occurs when there is selection against recessive or partially recessive detrimental [[allele]]s as they are expressed in the [[zygosity|homozygous state]].<ref name = Dussex2021/>