Kakapo

Identificación

The kākāpō is a large, rotund parrot. Adults can measure from 58 to 64 cm (23 to 25 in) in length with a wingspan of 82 cm (32 in). Males are significantly heavier than females with an average weight of 2 kg (4.4 lb) compared with just 1.5 kg (3.3 lb) for females. Kākāpō are the heaviest living species of parrot and on average weigh about 400 g (14 oz) more than the largest flying parrot, the hyacinth macaw.<p>The kākāpō cannot fly, having relatively short wings for its size and lacking the keel on the sternum (breastbone), where the flight muscles of other birds attach. 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.<p>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 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 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, 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.<p>Females are easily distinguished from males as they have a narrower and less domed head, narrower and proportionally longer beak, smaller cere and 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.<p>The kākāpō's 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.<p>Like many other parrots, kākāpō have a variety of calls. As well as the booms (see below for a recording) and chings of their mating calls, they will often loudly skraark.<p>The kākāpō has a well-developed sense of smell, which complements its nocturnal lifestyle. It can distinguish between odours while foraging, a behaviour reported in only one other parrot species. 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. One of the most striking characteristics of the kākāpō is its distinct musty-sweet odour. The smell often alerts predators to the presence of kākāpō.<p>As a nocturnal species, the kākāpō has adapted its senses to living in darkness. Its optic tectum, nucleus rotundus, and 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.<p>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.<p>The 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.<p>Because kākāpō passed through a 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. Beginning in 2015, the Kākāpō 125+ project has sequenced the genome of all living kākāpō, as well as some museum specimens. The project is a collaboration led by Genomics Aotearoa and a collaboration with a team of international collaborators.<p>A 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. 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 mutations compared to the number in mainland individuals. 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 purifying selection that occurred since the isolation of this population from the mainland about 10,000 years ago. Purging of deleterious mutations occurs when there is selection against recessive or partially recessive detrimental alleles as they are expressed in the homozygous state.

Taxonomía

The kākāpō was formally described and illustrated in 1845 by the English ornithologist George Robert Gray. He created a new genus and coined the binomial name Strigops habroptilus. Gray was uncertain about the origin of his specimen and wrote, "This remarkable bird is found in one of the islands of the South Pacific Ocean." The type location has been designated as Dusky Sound on the southwest corner of New Zealand's South Island. The generic name Strigops is derived from the Ancient Greek strix, genitive strigos ("owl"), and ops ("face"), while its specific epithet habroptilus comes from habros ("soft"), and ptilon ("feather").<p>In 1955 the International Commission on Zoological Nomenclature (ICZN) ruled that the genus name Strigops was feminine. The epithet habroptilus is an adjective, and under the rules of the ICZN the feminine form habroptila should be used when combined with the feminine genus name Strigops. The spelling of the binomial name therefore differs from that proposed by Gray and becomes Strigops habroptila. The species is monotypic, as no subspecies are recognised.<p>The name kākāpō is Māori, from kākā ("parrot") + pō ("night"); the name is both singular and plural. "Kākāpō" is increasingly written in New Zealand English with the macrons that indicate long vowels. The correct pronunciation in Māori is [kaːkaːpɔː]; other colloquial pronunciations exist, however. These include the British English /ˈkɑːkəpoʊ/ (KAH-kə-poh), as defined in the Chambers Dictionary in 2003. <p>The kākāpō is placed in the family Strigopidae together with the two species in the genus Nestor, the kea (Nestor notabilis) and the kākā (Nestor meridionalis). The birds are endemic to New Zealand. Molecular phylogenetic studies have shown that the family Strigopidae is basal to the other three parrot families in the order Psittaciformes and diverged from them 33–44 million years ago. The common ancestor of the kākāpō and the two Nestor species diverged 27–40 million years ago.<p>Earlier ornithologists felt that the kākāpō might be related to the ground parrots and night parrot of Australia due to their similar colouration, but this is contradicted by molecular studies; rather, the cryptic colour seems to be adaptation to terrestrial habits that evolved twice convergently.

Nombre científico

Strigops habroptilus

Autoridad

Gray, GR, 1845

Orden

Psittaciformes

Familia

Strigopidae

Género

Strigops

Distribución y hábitat

Before the arrival of humans, the kākāpō was distributed throughout both main islands of New Zealand. Although it may have inhabited Stewart Island / Rakiura before human arrival, it has not been found in the extensive fossil collections from there. Kākāpō lived in a variety of habitats, including tussocklands, scrublands and coastal areas. It also inhabited forests dominated by podocarps (rimu, mataī, kahikatea, tōtara), beeches, tawa, and rātā. In Fiordland, areas of avalanche and slip debris with regenerating and heavily fruiting vegetation – such as five finger, wineberry, bush lawyer, tutu, hebes, and coprosmas – became known as "kākāpō gardens".<p>The kākāpō is considered to be a "habitat generalist". Though they are now confined to islands free of predation, they were once able to live in nearly any climate present on the islands of New Zealand. They survived dry, hot summers on the North Island as well as cold winter temperatures in the sub-alpine areas of Fiordland. Kākāpō seem to have preferred broadleaf or mountain beech and Hall's tōtara forest with mild winters and high rainfall, but the species was not exclusively forest-dwelling.

Migración

Especie residente

Comportamiento

Patrón migratorio: Especie residente.

Conservación

Tendencia poblacional: en aumento.

Tendencia poblacional

en aumento