North Island kokako
Callaeas wilsoni (Bonaparte, 1851)
Other names: blue-wattled crow, kōkako, hokako, honga, onga, honge, onge, pakara, werewere
Geographical variation: Sometimes considered conspecific with South Island kokako C. cinerea, which has name priority.
With their extraordinary haunting song, and obscure evolutionary relationships to other birds, kokako evoke the forests of ancient New Zealand/Aotearoa perhaps more than any other species. More likely to be heard than seen, North Island kokako have persisted in small populations particularly in the central North Island from the King Country through to Te Urewera. They typically inhabit tall native forest dominated by tawa (Beilschmiedia tawa), singing from tree-tops but often feeding in understorey layers.
All mainland North Island populations persist only with sustained control of key pest mammals (ship rats and brushtail possums). All unmanaged populations are extinct.
The North Island kokako is a large songbird with a blue-grey body, a striking black mask and small, rich blue wattles that arise from the base of the bill and sit under the throat. Typically, when seen backlit in forest, kokako seem dark-plumaged and neither mask nor wattles are seen. They have long, strong legs and a long down-curved tail. Kokako characteristically bound and run among branches, interspersed with glides on short, rounded wings. They are usually located by listening for song and calls. The sexes are alike; juveniles have pink or lilac wattles. A few adults have orange wattles (cf. South Island kokako).
Voice: rich, sonorous, sustained, organ-like notes are sung by both male and female North Island kokako, frequently as duet, and typically from a high perch. There is a frequent close contact call of ‘took’, repeated variably.
Similar species: tui have similar silhouette and song (especially when mimicking kokako where they coexist), but they are much smaller, darker and more adept fliers, with very different head and throat ornamentation. Vagrant black-faced cuckoo-shrike from Australia is half the size, paler grey, lacks wattles, and is a bird of open woodlands, parks and gardens rather than dense native forest.
Distribution and habitat
Natural remnant North Island kokako populations are confined to a few scattered forests in the northern half of the North Island, particularly in the Waikato, Bay of Plenty, Te Urewera, South Auckland and Northland. Since 1981, has been successfully translocated to Little Barrier, Kapiti and Tiritiri Matangi Islands, Mount Bruce Scenic Reserve (Wairarapa), Boundary Stream Mainland Island (Hawkes Bay), Ngapukeriki (East Cape), Ark in the Park (Waitakeres, west Auckland), Whirinaki and Otanewainuku (Bay of Plenty), Maungatautari (Waikato) and Puketi (Northland). They characteristically reside in tall, diverse native forest, usually with a canopy of tawa or taraire with emergent podocarps or kauri. Kokako have successfully bred in planted diverse shrub- and tree- hardwoods on Tiritiri Matangi Island.
The North Island kokako population has increased from c.330 pairs in 1999 to c.1595 in 2017 due to pest control at key sites, and translocation. The largest populations, with more than 100 pairs each, are in Pureora Forest, Hauturu (Little Barrier Island ), Te Urewera, and Mapara (Waikato). Other large populations (> 50 prs) are at Mataraua/Waima (Northland), Hunua Ranges, Kaharoa-Onaia and Rotoehu near Rotorua, and there are 14 other smaller populations. Breeding pairs and unpaired singles defend 4-25 ha territories year-round by singing, which limits density.
Threats and conservation
Predation at nests by ship rats and possums is the primary cause of current declines of North Island kokako. Food reduction mainly by possums and predation by stoats are unhelpful secondary factors. All current populations must be continually managed against introduced mammal pests, either by repeated pest control on the mainland, or by vigilance against pest invasion on islands. Ship rats and possums are routinely targeted by trapping and poisoning so that their numbers are low for the duration of the breeding season (November to February). Food supply influences the number of breeding attempts that kokako make, but nest predators determine the outcomes of these attempts. Several key populations are being restored primarily by community groups. Maintenance of genetic health also influences management; e.g. new populations are established with individuals from two different source populations, totalling >40 founders. The conservation status of this species was moved from nationally vulnerable to 'at risk - recovering' in 2013.
North Island kokako typically raise one brood during November-February, after which they moult. In occasional years of good food supply, the breeding season may last 6 months and up to three broods can be raised. Two-four pinkish-grey eggs are laid in cup nests c.13 m (range 3-25 m) up trees. Incubation is by the female alone for c.18 days. Both adults feed the nestlings. Young fledge at 32-37 days old, and so nests are vulnerable to predation for about 7 weeks. Fledged young usually remain in parents' territory for a few months, up to a year, and continue to be fed by both parents.
Behaviour and ecology
North Island kokako defend large territories year-round by complex singing, including the longest known duetting of any songbird in the world. They are poor fliers; they usually bound around trees with their strong legs and with small wingflaps, but may glide some hundreds of metres down gullies from treetops. Net natal dispersal is usually c.1.4 km, but juveniles travel many kilometres around local territories before settling. Kokako populations are easily isolated by forest fragmentation. The tall forests they inhabit and their alert and skulking behaviour mean that most kokako are detected by their song and other vocalisation, frequently delivered from the tops of tall trees at dawn. Birds are captured by attracting them to mist-nets with playback.
North Island kokako mainly eat fruit and leaves and, less often, flowers, moss, buds, nectar and invertebrates.
Ewen, J.G.; Flux, I.; Ericson, P.G.P. 2006. Systematic affinities of two enigmatic New Zealand passerines of high conservation priority, the hihi or stitchbird Notiomystis cincta and the kokako Callaeas cinerea. Molecular Phylogenetics and Evolution 40: 281-284.
Flux, I.; Bradfield, P.; Innes, J. 2006. Breeding biology of North Island kokako (Callaeas cinerea wilsoni) at Mapara Wildlife Management reserve, King Country, New Zealand. Notornis 53: 199-207.
Higgins,P.J.; Peter, J.M.; Cowling, S.J. (eds.) 2006. Handbook of Australian, New Zealand and Antarctic birds. Vol. 7, boatbill to starlings. Oxford University Press, Melbourne.
Innes, J.; Hay, R.; Flux, I. Bradfield, P.; Speed, H.; Jansen, P. 1999. Successful recovery of North Island kokako Callaeas cinerea wilsoni populations, by adaptive management. Biological Conservation 87: 201-221.
Innes, J.; Molles, L.E.; Speed, H. 2012. Translocations of North Island kokako, 1981-2011. Notornis 60: 107-114.
Robertson, H.A; Baird, K.; Dowding, J.E.; Elliott, G.P.; Hitchmough, R.A.; Miskelly, C.M.; McArthur, N.; O’Donnell, C.F.J.; Sagar, P.M.; Scofield, R.P.; Taylor, G.A. 2017. Conservation status of New Zealand birds, 2016. New Zealand Threat Classification Series 19. Wellington, Department of Conservation. 27p.
Innes, J. 2013 [updated 2017]. North Island kokako. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
North Island kokako
- Social structure
- Breeding season
- Nest type
- raised platform
- Nest description
- Cup, varying from complex constructions with diverse vegetation placed on a large twig platform to simple scrapes on epiphyte clumps; both lined with tree-fern scales.
- Nest height (mean)
- 13 m
- Nest height (min)
- 2 m
- Nest height (max)
- 38 m
- Maximum number of successful broods
- Clutch size (mean)
- Clutch size (min)
- Clutch size (max)
- Mean egg dimensions (length)
- 38.55 mm
- Mean egg dimensions (width)
- 26.04 mm
- Egg colour
- Pinkish grey, irregularly splotched with brown and purple-brown mainly at larger end.
- Egg laying dates
- Incubation behaviour
- female only
- Incubation length (mean)
- 18 days
- Nestling type
- Nestling period (mean)
- 32-37 days
- Nestling period (min)
- 27 days
- Nestling period (max)
- 42 days
- Age at fledging (mean)
- 32-37 days
- Age at fledging (min)
- 27 days
- Age at fledging (max)
- 42 days
- Age at independence (mean)
- Several months
- Age at independence (min)
- 1 days
- Age at independence (max)
- 365 days
- Age at first breeding (typical)
- 1-2 years
- Age at first breeding (min)
- 1 years
- Maximum longevity
- Little known, perhaps 20 years
- Maximum dispersal
- Of juveniles: 5.4 km, but mean 1.4 km