New Zealand king shag
Leucocarbo carunculatus (Gmelin, 1789)
Other names: king shag, kawau, New Zealand king cormorant, rough-faced shag, carunculated shag, Marlborough Sounds shag, Cook Strait cormorant
Geographical variation: Nil
The New Zealand king shag is the only endemic bird species in the Marlborough Sounds. Although subfossil bone deposits indicate a possible former wide distribution, king shags have been confined to the outer Marlborough Sounds for at least 240 years. European naturalists first encountered king shags when J.R. Forster collected one in Queen Charlotte Sound during Captain Cook’s second visit to New Zealand, in May 1773. The small population has remained stable in distribution and numbers ever since.
The king shag is a large black-and-white shag with big pink feet. The black plumage on the head extends to just under the bill, making king shags appear dark-headed compared to the similar-sized pied shag. The uppersurfaces are black apart from a white patch or stripe near the leading edge of the inner wing. Some birds also have a white patch on the upper back. These white feathers are prominent on roosting birds, creating an elongated white patch in the middle of the otherwise black folded wing. Breeding adults have a patch of sulphur-yellow warty ‘caruncles’ on each side of the upper bill base; the size and colour intensity of these is reduced at other times of the year. The cobalt blue eye-ring is shared with other pink-footed ‘subantarctic’ shags, providing this group with the generic, but technically incorrect, name ”blue-eyed shags”. Juvenile birds are dull brown rather than black dorsally, and have pale facial skin.
Voice: croaking bursts of low frequency sounds, more intensive during the early morning.
Similar species: pied shags are similar in size, but have a predominantly white face, with the eye surrounded by white; they also lack any white feathers on the upperwings and back. Pied shags are also slimmer, compared to the thick-necked look of king shags.
Distribution and habitat
King shags are restricted to the outer Marlborough Sounds, from the west coast of D’Urville Island east to the northern end of Arapawa Island. The area occupied is about 60 x 30 km. There are 8-10 breeding sites per annum, but over 90% of the population breeds at four sites: Trio Islands, Duffers Reef, White Rock, and Sentinel Rock. King shags can occasionally be seen from the interisland ferry, usually near where Tory Channel joins Queen Charlotte Sound. Away from the Marlborough Sounds, there are possible records of single king shags from Wellington Harbour (July 2002), and Kaikoura (October 2011).
King shags breed on low rock plateaus (Duffers Reef and Stewart Island), steep rock faces (Trio Islands and White Rock) or rock ridges (Sentinel Rock and Rahuinui Island). Most birds forage to the west, south or south-east of their colonies. Foraging directions are influenced by wind direction, with birds utilising wind assistance to bring food back to their chicks.
The king shag population is estimated at about 645 birds, and has apparently been stable for at least the past 50 years, and possibly over 100 years.
Threats and conservation
The restricted distribution and small population size of king shags means that a single adverse event, such as an oil spill, could impact most of the population. Other risks include coastal eutrophication impacting the deep benthic communities where the shags feed, or causing toxic algal blooms. King shags are vulnerable to disturbance at their colonies, and use of set-nets (particular in close proximity to colonies).
Most king shag breeding activity occurs during winter. Nests are platforms of sticks and seaweed, cemented with guano. The 1-3 pale blue eggs are usually laid in May-June. There is no information on incubation length or nestling period, but juveniles are present at colonies from July onwards. Adults feeding chicks depart colonies at sunrise, arriving back at the colony about midday. About 102-126 pairs breed per annum, producing 40-68 juveniles. Duffers Reef is the most productive breeding site.
Behaviour and ecology
King shags are difficult to study due to their inaccessible breeding sites and sensitivity to disturbance. Most studies have been boat-based, looking at patterns of bird movements to and from colonies, and activity of king shags around marine farms. The low number of pairs attempting to breed each year suggests that king shags are not annual breeders, or have extremely delayed maturity.
King shags are deep divers, feeding on bottom-dwelling fish species at depths of 20-50 m.
The most important prey item is witch (Arnoglossus scapha), a left-eyed flatfish. Witch comprised 90% of king shag prey items and 95% of wet mass in one study. Witch is the most common species of flatfish in New Zealand, occurring from shallow waters to depths of over 400 m; it is most common in deeper water with coarse-grained sediments. Other important prey species include lemon sole (Pelotretis flavilatus) and opalfish (Hemerocoetes monopterygius). All the preferred prey items are bottom-dwelling species, highlighting the king shag’s deep diving abilities and dependence on a healthy benthic environment in the deeper waters of the Marlborough Sounds.
Brown, D. 2001. Dive duration and some diving rhythms of the New Zealand king shag (Leucocarbo carunculatus). Notornis 48: 177-178
Heather, B.D.; Robertson, H.A. 1996 (rev 2000). The field guide to the birds of New Zealand. Viking, Auckland.
Lalas, C.; Brown, D. 1998. The diet of New Zealand king shags (Leucocarbo carunculatus) in Pelorus Sound. Notornis 45:129-140.
Marchant, S.; Higgins, P.J. (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1, ratites to ducks. Oxford University Press: Melbourne.
Robertson, C.J.R. et al. 2006. Atlas of bird distribution in New Zealand 1999-2006. Ornithological Society of New Zealand, Wellington.
Schuckard, R. 1994. New Zealand king shag (Leucocarbo carunculatus) on Duffers Reef, Marlborough Sounds. Notornis 41: 93-108.
Schuckard, R. 2006. Population status of the New Zealand king shag (Leucocarbo carunculatus). Notornis 53: 297-307.
Taylor, G. 2000. Action plan for seabird conservation in New Zealand. Part A: threatened seabirds. Threatened Species Occasional Publication No.9. Department of Conservation. New Zealand.
Tennyson, A.J.D. 2010. Pelecaniformes. Pp. 138-15. In: Checklist Committee (OSNZ) 2010. Checklist of the birds of New Zealand, Norfolk and Macquarie Islands, and the Ross Dependency, Antarctica (4th ed.). Ornithological Society of New Zealand & Te Papa Press, Wellington.
Schuckard, R. 2013. New Zealand king shag. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
New Zealand king shag
- Social structure
- Breeding season
- Nest type
- cliff ledge, raised platform
- Egg colour
- Chalky white with creamy background
- Egg laying dates
- Interval between eggs in a clutch
- Unknown days
- Incubation behaviour
- Incubation length (mean)
- Nestling type
- Nestling period (mean)
- Age at fledging (mean)
- Age at independence (mean)
- Age at first breeding (typical)
- Maximum longevity
- Maximum dispersal
- Unknown if there is exchange between colonies