ASIGNATURA ACTITUD

Kakapo belong to the world’s oldest parrot family (Wright et al. 2008). Much controversy has oc- curred over the years as whether to place the genera Strigops (S. habroptilus) and Nestor (kea, N. meridionalis and kaka, N. notabilis) independently from each other or to unite them within the fam-

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ily of Nestoridae. New molecular data and analyses, though, place the two subfamilies Strigopinae and Nestorinae in a single sister clade. Hence, within the avian order Psittaciformes the kakapo is considered to have formedalongside the two sister subfamilies kea andkaka. Together these spe- cies form a distinct parrot family: the Nestoridae (De Kloet & De Kloet 2005; Astuti et al. 2006; To- kita et al. 2007; Wright et al. 2008; Gill et al. 2010; Mayr 2010). This family is likely to have diverged from that of all other parrots during the Cretaceous some 80 million years ago, coinciding with New Zealand’s geographical separation and isolation from Gondwanaland.

Understanding the geological history of New Zealand is important since it has contributed to a unique fauna. Isolated from the rest of the world for more than 80 million years and in the absence of mammalian predators, New Zealand’s avifauna is characterised by having more flightless birds than any other place in the world (Wilson 2004). Many New Zealand birds distinguish themselves through peculiar mammal-like habits. Each bird for example filled ecological niches typically taken by mammals elsewhere: moa and kakapo as ‘forest browsers’, takahe as ‘grass eaters’, kiwi, as the `honorary mammal’ and wrens as ground ‘insect eaters’. Hence, it is not surprising that New Zea- land sets itself apart by having a bird fauna with a high level of endemism’. 133 birds species occur only in New Zealand, with 87% of all terrestrial birds and 44% of all breeding seabirds being en- demic (Wilson 2004). Many New Zealand birds are remarkable for having a number of unique char- acteristics. Gigantism (or dwarfism as in kiwi (Apterygidae)) is one of them; a feature observed in many island habitats, where constraints related to predation and / or competition, for instance, are removed (Lomolino 2005). Kakapo are a clear example of gigantism and are the largest parrot spe- cies in the world.

Although their dimorphism is not overtly obvious, female kakapo are smaller with an adult body- weight of 2-2.5 kg compared to males which can reach 3.5 to 4 kg (Elliott et al. 2001; Eason et al.

2006). Female’s heads are slimmer and proportionally longer than males. The female’s beak is slightly narrower than the male’s, and they have smaller nares. The female’s plumage is moss green with slightly brownish and yellowish spots, giving them a vaguely more yellowish colouration than males. Their feet are also slender compared to males and they have a comparatively longer tail (Higgins 1999). The most reliable way to physically sex birds regardless of their age is through the colouration of the four outermost primary feathers on their wings. While in males the lower side of the four outermost primary feathers is mottled with a vague water-mark pattern to the tips, in fe- males there are no such marks (Powlesland et al. 2006). Both sexes have a facial disc orientated like owls, which earned them the moniker “owl parrot”. Their cryptically coloured plumage perfectly

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merges with the foliage so that they are hard to spot. Kakapo remain motionless to avoid being de- tected when approached (Morris 1977; Powlesland et al. 2006). Due to the long absence of mam- malian predators many New Zealand bird species, including kakapo, have not developed a typical fear response (Brown et al. 1999, Laundré et al. 2010), but instead freeze when exposed to a poten- tial danger (Morris 1977; Whitwell 2009).

Even though kakapo are well camouflaged, they are considered to have become nocturnal due to predation from the air (Williams 1956; Wilson 2004). This idea is supported by the plumage colour- ation of the closely related kea, known for its bright, orange red underwings, which are only visible from below when the wings are extended, while from the top this bird is perfectly well camou- flaged. Historically avian predators would have included the Haast eagle (Harpagornis moorei) and the Eyles harrier (Circus eylesi) (Holdaway & Worthy 1997), both of which are extinct today. It can be assumed that nocturnality in kakapo appeared after the split from kea and kaka, which both are diurnal but can also be active at night (pers. comm. R. Hitchmough and D. Brunton).

Kakapo still possess large wings but they cannot fly and Douglas Adams & Carwardine (1990) noted: “that not only has the kakapo forgotten how to fly, but it has also forgotten that it has forgotten how to fly“, denoting the fact that birds climb trees and attempt to flap to the ground. Flightless- ness is a feature kakapo share with more than half of New Zealand’s terrestrial avifauna (extinct and extant species). Flightlessness evolved several times independently among different lineages (Cooper et al. 1992). While the ratites evolved from flightless ancestors (Cooper et al. 1992), all other flightless birds have lost their ability to fly after their ancestors colonised New Zealand (Wil- son 2004). Due to the lack of mammalian predators many birds in New Zealand could afford to lose the power of flight (McNab 1994). For kakapo the loss of flight enabled this species to develop a larger body mass, which in thermodynamic terms is far more cost-effective. A large body size is also associated with a herbivorous diet and the need to spend more time foraging in order to meet their nutritional needs (Raubenheimer & Simpson 1999 and 2006).

Fossil fevidence and early observations of kakapo suggest they were abundant on the three main islands of New Zealand and inhabited a variety of vegetation types from sea level to alpine regions. They were considered most common in rimu (Dacrydium cupressinum) and beech (Nothofagus sp.)

forestsin areas of high rainfall (Worthy & Holdaway 2002; Wood 2006). Kakapo were not exclusively forest-dwelling since historic accounts often associate kakapo with grasslands (Henry 1903; Worthy

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& Holdaway 2002). Kakapo are currently confined to a few offshore islands and the species has only survived due to enormous conservation efforts.

Kakapo are exclusively herbivorous and feed on bark, twigs, leaves, seedlings, nectar, fruit, ferns, rhizomes and fungi (Haast 1864; Potts 1873; Henry 1895; Pascoe 1957; Best 1984; Butler 2006). Like all parrots, kakapo use their feet to hold food. Their strong feet are also used to excavate subterra- nean and nutritious bulbs, tubers, corms and rhizomes (Best 1984). Females, due to their smaller size and lighter weight, are more agile and thus are thought to benefit by reaching the outer branches of trees that hold most of the fruit (Henry 1903; Powlesland et al. 2006). Using their pow- erful beak and short but strong tongue, kakapo generally squeeze vegetable material against the ridged upper palate allowing the plant juices to be extracted. All other food is finely ground with the help of the lower mandible and large, keratinised regions on the tongue. Unlike kea and kaka, the kakapo’s tongue is not adapted for collecting nectar (Kirk et al. 1993).

Kakapo are solitary year round and occupy large home ranges (Reischek 1890). Studies on home range size in kakapo have found considerable variation (Burt 1943; Best 1984). Male home range size varies between 26 and 50 ha and can include their ‘track and bowl’ mate attraction system. Females have home ranges approximately 10 - 20 ha larger than those of males. Female home ranges are located between male ranges but in general some distance from the ‘track and bowl’ systems (Moorhouse 1985; Cockrem 1989; Farrimond et al. 2006a). There is a correlation between breeding success and the size and quality of female home ranges; additionally, quality home ranges tend to include abundant rimu forest (Whitehead 2007; Whitehead et al. 2012).