Data Zone
Justification of Red List category
This species has a small population size of less than 1,000 mature individuals. It is therefore classified as Vulnerable.
Population justification
Surveys between 1992 and 2002 indicate a population of c.645 birds, including 102-126 breeding pairs (Schuckard 2006). Aerial surveys in 2015 recorded 839 birds in February 2015 and 187 breeding pairs in June 2015 (Schuckard et al. 2015). Improvements of survey methods are the predominant reason to explain perceived differences in numbers with earlier surveys. Robertson et al. (2021), assessing the species according to criteria elucidated in Townsend et al. (2008), placed its population in the band 250-1,000 mature individuals. In 2020, the population was estimated to number c.300 breeding pairs (Robertson et al. 2021). Hence, a population of 250-999 mature individuals is assigned here. This equates to 375-1,499 individuals in total, rounded here to 350-1,500 individuals.
Trend justification
The population trend is believed to have been stable over the last 50 years (Schuckard 1994, 1998, 2002; Robertson et al. 2021).
Leucocarbo carunculatus is endemic to New Zealand, where about 85% of the population occupies five colonies on White Rocks, Sentinel Rock, Duffers Reef, North Trio and Rahuinui Island (Bell 2010). Also in the Marlborough Sounds, smaller breeding colonies occur on Stewart Island, Tawhitinui, Hunia Rock and The Twins (Schuckard et al. 2018).
The species breeds on small islets and rock stacks, with nests on all known colonies spaced c.1 m apart (Schuckard et al. 2015). Otolith samples were collected in 2011 from four colonies. A total of seventeen species of fish and dwarf octopus have been identified in the pellets from four colonies: Witch (Arnoglossus scapha), Lemon Sole (Pelotretis flavilatus), opalfish (Percophidae), Scorpionfish (Helicolenus percoides), True Sole (Peltorhamphus) and triplefin (Tripterygiidae) (Schuckard 2013). The maximum feeding distance is 25 km (Schuckard 2013).
Interactions with the fishery pose a serious threat to this species. According to Rowe (2010), set-net fisheries represent the greatest risk to seabirds in this area, causing widespread and permanent damage with local extinction or serious population declines. Set-nets are sometimes placed very close to colonies (Schuckard 1994) and present a major risk. Direct persecution is also reported, with fishermen and fish farmers illegally shooting shags because they are considered competitors (Taylor 2000, Butler 2003).
Human disturbance by boats, aircrafts and scuba divers can cause desertion of nests and subsequent chick predation by gulls Larus spp. (Nelson 1971, Schuckard 1994). Nesting birds are highly susceptible to disturbance by boats and low-flying aircrafts and may abandon eggs or chicks as a result (Butler 2003). However, other studies suggested that boat traffic had less impact on the Rough-faced Shag than on other species; escape by diving (rather than flying) reduced the interruption to foraging, and hence was considered unlikely to have significant impacts on their foraging and resting activities. The establishment and subsequent growth of the Stewart Shag Leucocarbo chalconotus colony in Otago Harbour despite regular boat traffic was considered evidence that this was not a significant detrimental factor to shag populations (Lalas unpubl. 2000 in Butler 2003). Growth in the tourism industry, as implied by new interest from tour operators in the species (Schuckard 1994), could increase the threat from human interference in the future.
An increased frequency of storms and flooding events associated with climate change poses a threat to the species. Schuckard et al. (2015) observed significant losses of nests following stormy weather. Nests are comprised of vegetation cemented together with guano and low-lying or otherwise exposed nests are particularly vulnerable to extreme weather events. It is not known whether this species lays replacement clutches, but this has been recorded in other Phalacracoracidae (Orta 1992 in Schuckard et al. 2015).
Oil spills is another potential threat which could have severe impacts on the population. The risk of spillage is moderately high owing to the large volume of petroleum-products being shipped through Cook Strait and in the Marlborough Sounds (Taylor 2000).
Concerns about change of benthic habitat from various activities like land run-off and both mussel and other aquacultures may have impact on the distribution and abundance of prey. Conservation management should take into account this species' relic distribution and low genetic diversity (Rawlence et al. 2017).
Conservation Actions Underway
All permanent colonies are wildlife sanctuaries, and are sign-posted. Charter boats have to remain 50-100 m from colonies, but it is thought that this may not be sufficient to avoid considerable disturbance (Schuckard 1994). House Rats Rattus rattus briefly colonised Duffers Reef, but were eradicated by 1983 (Taylor 2000). In 2015, a Rough-faced Shag Management Plan was published as part of granting consent of two more salmon farms in the feeding area (Schuckard 2015). Recognition of the feeding areas of the species (1300 km2, 25 km from main colonies) is overdue.
Conservation Actions Proposed
Census all breeding colonies every five years using an established methodology (Taylor 2000). Develop techniques for establishing colonies at new sites. Establish a code of conduct for commercial charter boat operators and fishers to minimise the disturbance of colonies. Obtain protection for all breeding grounds (Taylor 2000). Prevent marine farming close to colonies and avoid further physical and benthic footprint overlap with feeding areas (R. Schuckard in litt.). Create marked populations to identify potential population structure of species. Identify individual preference of feeding areas through telemetry. Start an advocacy programme to encourage fishers to adopt set-net practices which minimise bycatch (Taylor 2000).
76 cm. Large, black-and-white cormorant. Black head, hind neck, lower back, rump, uppertail-coverts, all with metallic blue sheen. White underparts. Pink feet. White patches on wings appear as bar when folded. Yellow-orange caruncles above base of bill. Similar spp. Pied cormorant P. varius has white face, neck, black feet, no white patches on wings. Voice Makes little noise at colonies, silent elsewhere.
Text account compilers
Vine, J.
Contributors
Benstead, P., Fjagesund, T., Mahood, S., Martin, R., McClellan, R., Miller, E., Pilgrim, J., Schuckard, R. & Taylor, J.
Recommended citation
BirdLife International (2024) Species factsheet: Rough-faced Shag Leucocarbo carunculatus. Downloaded from
https://datazone.birdlife.org/species/factsheet/rough-faced-shag-leucocarbo-carunculatus on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.