Strigopidae

Diversity

The family Strigopidae , commonly known as New Zealand Parrots, consists of two extant genera, Nestor and Strigops . Genetic evidence has shown that Strigopidae is sister to all other Psittaciformes . Nestor includes two extant species, the kea and the kaka, the latter of which contains two subspecies: Nestor meridionalis meridionalis and Nestor meridionalis septentrionalis . Strigops contains one extant species, the kakapo.

The family also includes a number of extinct taxa, including Nestor productus , Nestor chathamensis , and Nelepsittacus .

This unique group of birds are endemic to New Zealand and are extremely vulnerable to shifting climates, invasive species, and habitat loss and fragmentation. They are of interest to researchers due to their apparent relationship to other parrots as well as their high level of intelligence.

Geographic Range

Members of Strigopidae are found on both the north and south island of New Zealand, to which they are endemic. They are found primarily on the northwest coast of the southern island, although some are present in the inland of the north island. With the exception Nestor notabilis , they are non-migratory and occupy the same range year-round.

Strigops habroptila are found on only three islands: Whenua Hou, Anchor Island and Hauturu. Predation from introduced mammals led to extirpation from other areas of their native range.

N. notabilis undergo a small, yearly migration to take advantage of variable food resources, which is also reflected in their diet.

• Biogeographic Regions
• oceanic islands oceanic islands
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Members of the family Strigopidae occupy temperate forests throughout New Zealand. Notably, they can be found in Nothofagus forests.

Nestor notabilis is known for its range, which extends into the subalpine regions of the southern island. They migrate throughout an elevation gradient in pursuit of food. During the summer, they occupy upper scrub and grassland zones. In the autumn, they move higher to feast on berries, before moving below the timberline for the winter. They have also been observed congregating near ski lodges during the winter to take advantage of human food waste.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• scrub forest scrub forest
• mountains mountains

• Other Habitat Features
• urban urban

Systematic and Taxonomic History

Nestor is monotypic, with no known synonyms.

Strigops habroptila was originally known as Strigops habroptilus , until 1955 when the ICZN formally femininized the specific epithet.

Nestor notabilis and Nestor meridionalis are sister to each other. Nestor meridionalis has two subspecies, Nestor meridionalis meridionalis and Nestor meridionalis septentrionalis .

Nestor is sister to Strigops .

Strigopidae is sister to Psittaciformes .

Physical Description

Members of the family Strigopidae are large parrots with brown to green plumage. Weights range between 550 up to 3000 grams. New Zealand Kaka Nestor meridionalis make up the lighter end of this scale, with kakapos Strigops habroptila at the far end, making them the largest parrot species in the world. Measurements range between 45 to 64 centimeters in length.

Species in the genus Nestor exhibit some level of sexual dimorphism, with females being slightly smaller and having a shorter, less curved beak. They are notable for having striking orange and red plumage that is particularly prominent during flight. Female kakapos weigh less than males, but are otherwise identical.

New Zealand Kaka consists of two subspecies: North New Zealand Kaka Nestor meridionalis septentrionalis and South New Zealand Kaka Nestor meridionalis meridionalis . They are morphologically distinct, with the North island subspecies having a darker crown and overall less vibrant plumage.

• Sexual Dimorphism
• sexes alike
• male larger
• sexes shaped differently

Reproduction

Keas ( Nestor notabilis ) are monogamous and form long-term pair-bonds. Breeding adults may join flocks of juveniles when they pass through their home range and form flexible hierarchies.

New Zealand Kakas ( Nestor meridionalis ) are monogamous. Additionally, they are episodic breeders who reproduction is influences by food availability. They may mate multiple times per breeding season to produce multiple clutches.

Kakapos ( Strigops habroptila ) are polygynous and solitary, only coming together during breeding season. Kakapos are notable for lekking, where males use a loud "boom" call to attract females. Like Nestor meridionalis , kakapos are episodic breeders that depend on food availability. Breeding is associated with the fruiting of rimu and southern beech trees, which occurs every 2-4 years.

• Mating System
• monogamous monogamous
• polygynous polygynous

Strigopidae species vary in their breeding season and incubation period. They each lay 1-5 eggs, with 4 being typical for Nestor and 2 being typical for Strigops .

Keas ( Nestor notabilis ) breed throughout July to January. Incubation lasts 22-24 days and chicks remain in the nest for 3 months before fledging from December-February. Females typically lay one clutch per year. Some may lay successively, but not all females lay every year. N. notabilis are secondary cavity nesters, taking advantage of rock crevices, hollows at the base of large trees, under the roots of large trees, in hollow logs, and in dirt crevices.

New Zealand kakas ( Nestor meridionalis ) breed from September to March and incubate their eggs for 3 weeks. They are also secondary cavity nesters who nest in the trunks or limbs of trees. Cavities may be used across multiple breeding seasons. Chicks fledge when they are 70 days old. Females are known to mate multiple times throughout the breeding season and may have two clutches of eggs per season.

Strigops habroptila individuals breed from December to February. Incubation lasts around 1 month and chicks remain in the nest for 3.5 months. They nest in shallow depressions on the ground, usually concealed by dense vegetation, or in secondary cavities such as at the bases of trees.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• fertilization fertilization
  • internal internal

As solitary birds, kakapo chicks are exclusively cared for by the female, with the male only coming into contact with the female during breeding. Chicks are fed regurgitated plant matter and preened by the female, who also maintains the cleanliness of the nest and defends it from intruders. Fledging is gradual, with chicks spending more and more time outside the nest until they eventually fail to return. The female continues to provide some food to the fledglings for at least three months after they leave the nest. Additionally, fledglings remain near the female's home range until they are up to eight months old, when they leave to establish their own territories.

New Zealand Kakas are the only member of Strigopidae to exhibit true male parental care. During incubation, the female is the only one to enter the nest, with her mate visiting often to feed her regurgitated food. Similarly, the chicks are fed only by the female during the nestling stage. Females are known to fight off predators that threaten her nest. As the nestlings age, the female spends more and more time away from the nest. Once fledged, chicks are fed by both the female and male.

Kea females exclusively participate in incubation, brooding, and feeding the chicks. The male feeds regurgitated food to the female. Juveniles spend time with unrelated adults, facilitating the learning of complex foraging behaviors.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-hatching/birth
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • female
• post-independence association with parents
• extended period of juvenile learning

Lifespan/Longevity

Kakapos have a mean lifespan of at least 60 years. They are thought to be the longest-lived bird species in the world, able to reach up to 90 years old. Keas have been known to reach up to 50 years old in captivity and 30 years old in the wild. New Zealand Kakas have lived up to 42 years old in captivity and anecdotal records indicate that they can live up to 27 years old in the wild.

Behavior

Kakapos are solitary as adults. They are flightless but are capable climbers and capable of running over short distances. Males gather prior to breeding season at traditional lekking sites. They are notable for being the only nocturnal parrot in the world. They maintain large territories that vary in size depending on population densities. In general, these territories range in size from 15-100 hectares.

Keas are strong fliers. Non-breeding juveniles form loose, wandering flocks. Breeding adults may occassionally join these flocks if they pass through their home range. Unrelated adults will tolerate the presence of juveniles, facilitating the learning of foraging skills. Keas are known to be among the smartest birds in the world.

New Zealand Kakas can be found in groups around food sources but are otherwise solitary. When gathered, they are quite loud and boisterous, often partaking in play. They are capable fliers.

• Key Behaviors
• arboreal arboreal
• scansorial
• terricolous
• flies
• glides
• diurnal diurnal
• nocturnal nocturnal
• migratory migratory
• solitary solitary
• territorial territorial

Communication and Perception

Members of Strigopidae communicate primarily through vocalizations. Each species within the family has specialized calls. Keas and kakas have a greater variety of vocalizations. Strigops habroptila males are known for "booming" to attract mates to their lek. The Maori people of New Zealand named the kea after its distinctive call.

• Communication Channels
• acoustic acoustic

Food Habits

Strigops habroptila is vegetarian, feeding from a variety of sources that varies throughout the seasons. Their general diet consists of fruits, berries, nuts, and seeds, as well as various parts of vegetation, including leaf buds, roots, rhizomes, tubers, bark, and stems. They also eat moss and fungi. Important food sources are Blechnum , Dracophyllum , Gahnia , Astelia , Lycopodium , Schizaea , Cyathodes , Olearia , Thelymitra , Oreobolus , and Carex . During the spring and summer, new growth is favored. Subterranean portions of the vegetation is favored during autumn and late spring.

Nestor notabilis diet varies throughout the year. In January, trees and shrubs, including Phormium colensoi and Metrosideros make up the majority of their diet. During late January until the first snowfall, Podocarpus nivalis berries are an important food source. The fruit of Coprosma ciliata , Cyathodes fraseri , Muehlenbeckia axillaris , Pentachondra pumila , Astelia nervosa , as well as the leaves of Senecio scorzoneroides consumed year round. Kea are also known to scavenge for flesh and bone marrow. They are also known for scavenging human trash.

Nestor meridionalis feeds on fruits, berries, seeds, flowers, buds, nectar, and invertebrates. Important sources include Podocarpus ferrugineus , Beilschmiedia tarairi , and Agathis australis . During the winter, the sap of Pseudopanax colensoi , Griselinia littoralis , Nothofagus solandri , Metrosideros umbellata , and Dacrydium cupressinum are consumed. Other important sources during the winter are Vitex lucens and Dysoxylum spectabile . In urban areas, the sap of Cupressus macrocarpa , Chamaecyparis lawsoniana , and Cryptomeria japonica is used. In Nothofagus forests, honeydew produced by Ultracoelostoma assimile is a critical food source during the winter. Additionally, the larva of Ochrocydus huttoni is a valuable source of protein.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • scavenger scavenger
• herbivore herbivore
  • folivore folivore
  • frugivore frugivore
  • granivore granivore
  • lignivore
  • nectarivore nectarivore

Predation

Strigopidae species are preyed upon primarily by introduced mammals, notably stoats Mustela erminea and brushtail possums Trichosurus vulpecula . Their native predators include birds of prey such as the New Zealand falcon Falco novaeseelandiae and the Australasian harrier Circus approximans .

Strigops habroptila exhibit cryptic coloration that allows them to blend in with the forest floor to avoid detection. Nestor species exhibit cryptic behavior, such as remaining still and beneath cover when threatened.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Kea Nestor notabilis are thought to be largely responsible for seed dispersal across the alpine ecosystems of New Zealand.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Strigopidae provide no direct economic benefit for humans. Indirect benefits include research and potentially ecotourism. Members of Nestor are studied for their high intelligence. Strigops habroptila is studied for its unique traits and the evolutionary implications of these traits.

• Positive Impacts
• ecotourism ecotourism
• research and education

Economic Importance for Humans: Negative

Nestor species are known for causing issues with locals due to their high intelligence, including property damage and general mischievous behavior.

Conservation Status

Strigopidae species are at risk of extinction. Striops habroptila is critically endangered, Nestor notabilis is endangered, and Nestor meridionalis is considered vulnerable.

The primary threat to these species is introduced terrestrial mammals. New Zealand has no native terrestrial mammals, meaning that these birds are not adapted to deal with these threats. Specifically, many of these mammals will predate nests, which are easily accessed due to the bird's reproductive traits.

Climate change is particularly threatening to N. notabilis 's habitat as increasing global temperatures lead to decreased habitat availability in the alpine.

Current efforts to combat population loss include breeding programs, habitat protection, and attempts to eradicate invasive species. Additional efforts to combat climate change also benefit this family.

Other Comments

Strigopidae species are of high cultural value to the native Māori people of New Zealand.

The common names for the species come from the Māori people.

Additional Links

Encyclopedia of Life

Contributors

Sam Voetberg (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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