VU
Stewart Shag Leucocarbo chalconotus



Justification

Justification of Red List Category
This species is classified as Vulnerable because it has a small range and is restricted to a small and decreasing number of colonies. Although it is known to abandon and reoccupy sites over decades, the loss of a comparatively large number of locations in recent years is of concern, and although population trends are unclear, the population may be declining.

Population justification
Population estimates have varied, although the population may be as high as 5,000-8,000 individuals (C. Lalas in litt. 1994). This is roughly equivalent to 3,300-5,300 mature individuals.

Trend justification
The species is suspected to be declining overall. The only national census dates from 1981, when the population was estimated at 1,800-2,000 breeding pairs, 900-1,000 in both Otago and Southland. The Otago population doubled to 1,850 pairs in 1987-1988, and the breeding range also expanded, but numbers then decreased to 1,500 pairs in 1992-1993 (Taylor 2000). In 1914, the population on Kane-te-toe Island was estimated at 400-500 nests; however, by 1975 the colony had been deserted (Watt 1975). The population on Centre Island declined from 600 to 25 nests between 1955 and 1991 (Taylor 2000). Colonies on Jacky Lee and Codfish Islands have also been deserted (B. Weeber in litt. 2000).

Distribution and population

Leucocarbo chalconotus is endemic to New Zealand, breeding on the South Island from the coast of North Otago south to Foveaux Strait, and on Stewart Island. In total, it breeds at c.9 localities (G. A. Taylor in litt. 2000) in colonies of 10-500 pairs (Heather and Robertson 1997).

Ecology

It breeds on rocky headlands and islands, building a platform nest of twigs, seaweed and guano, 0.5 m in diameter and 1-1.5 m high (Marchant and Higgins 1990, Heather and Robertson 1997). It appears to eventually destroy the surrounding vegetation, probably contributing to the abandonment of colonies until sufficient regeneration has occurred (Watt 1975). It feeds on fish and marine invertebrates (Heather and Robertson 1997). It disperses over shallow inshore waters within 15 km of land (G. A. Taylor in litt. 2000).

Threats

Entanglement in fishing equipment represents a major threat to the species, in particular set-netting near breeding colonies, which regularly traps individuals (Taylor 2000). Other fishing techniques (potting, line-fishing and trawling) represent a small risk to the species. Internationally, studies of shag interactions in pot and trap fisheries are limited, but Bell (2012) presents accounts of shag bycatch in the Chatham Islands lobster fishery. The species is occasionally directly targeted and illegally shot, because it is considered a competitor by fishermen and fish farmers (Taylor 2000). Human intrusion and disturbance may be another source of decline of the species; Watt (1975) described Stewart Shags at the Taiaroa Head colony readily deserting their nests in response to even mild degrees of human disturbance. Introduced predators such as mustelids, cats and rodents are a threat to mainland colonies (e.g. Taiaroa Head); however, most nesting colonies are situated on predator-free islands (Taylor 2000), hence the species as a whole is not currently threatened by invasive species.

Conservation actions

Conservation Actions Underway
Although only one national census has been completed, many counts have been made at individual colonies, mostly since the 1950s (Taylor 2000). All colony sites have been proposed as an IBA (Hand 2013).

Conservation Actions Proposed
Survey the species's entire range to locate and census all breeding colonies. Monitor at least one colony in Otago and Foveaux Strait yearly, and census the entire breeding population every 10 years. Develop techniques to establish new colonies. Fence colonies at mainland sites to exclude predators and stock. Develop an advocacy programme to discourage shooting. Encourage the safe use of set-nets in order to minimise bycatch, enforcing restrictions if necessary, near Stewart Island colonies (Taylor 2000). Prevent marine farming near breeding colonies and feeding areas (B. Weeber in litt. 2000). Obtain legal protection for all colonies (Taylor 2000).

Identification

68 cm. Large cormorant with pied and bronze phases. Pied phase, blackish head, upperparts with white patch on upperwings appearing as a bar when folded. White underparts. Pink feet. Orange caruncles. Bronze phase, all brownish-black with green-blue sheen. Voice Male calls at nest, silent away from colonies.

Acknowledgements

Text account compilers
Taylor, J., Wanless, R., van der Merwe, N., Mahood, S., Benstead, P., Martin, R., McClellan, R., Fjagesund, T., Miller, E., Moreno, R., Pilgrim, J.

Contributors
Weeber, B., Lalas, C., Taylor, G.A.


Recommended citation
BirdLife International (2019) Species factsheet: Leucocarbo chalconotus. Downloaded from http://www.birdlife.org on 24/05/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/05/2019.