Chlidonias albostriatus


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Chlidonias albostriatus
Species Authority: (Gray, 1845)
Common Name(s):
English Black-fronted Tern
Chlidonias albostriatus Collar and Andrew (1988)
Chlidonias albostriatus Collar et al. (1994)
Chlidonias albostriatus Sibley and Monroe (1990, 1993)
Sterna albostriata (Gray, 1845)
Taxonomic Notes: Chlidonias albostriatus (del Hoyo and Collar 2014) was previously placed in the genus Sterna as S. albostriata.

Assessment Information [top]

Red List Category & Criteria: Endangered A2bce+3bce+4bce ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Bell, B., Bell, M., Dowding, J., Grant, A., Hitchmough, R., Keedwell, R., Szabo, M. & Taylor, G.
Facilitator/Compiler(s): Anderson, O., Benstead, P., Bird, J., Butchart, S., Calvert, R., Mahood, S., McClellan, R., Pilgrim, J. & Taylor, J.
This tern has a small population which has shown recent very rapid population reductions at some wintering and breeding sites, which are predicted to continue in the future owing to on-going threats. It is therefore considered Endangered.

Geographic Range [top]

Range Description: Chlidonias albostriatus breeds in the South Island, New Zealand. It is found along the eastern riverbeds from Marlborough to Southland, and on the upper Motueka and Buller Rivers in southern Nelson (Heather and Robertson 1997). Birds disperse to the coastline and estuaries in winter, mostly from Stewart Island to the southern North Island, feeding at sea within 10 km of the coast (Heather and Robertson 1997, Taylor 2000). The most recent estimates put the total population at 7,000-10,000 individuals (R. Keedwell in litt. 2006) or 5,000 individuals (per M. Bell in litt. 2012). All populations of this species that have been studied have been in decline (G. A. Taylor in litt. 1999). Numbers recorded in the Bay of Plenty during winters in the 1980s ranged between 25 and 45 individuals. Since 2000, counts at the same site have varied between 10 and 16 individuals (M. Szabo in litt. 2006). Similarly, on the breeding grounds numbers on the Ashburton River declined from over 750 birds in 1981 to fewer than 200 by 1990 (O'Donnell 1992, Maloney 1999, Taylor 2000). A total of 55 individuals was recorded in the lower 18 km of the Ashley River in 1980 (Wildlife Service surveys), with just 26-28 along the same stretch in 2005-2006 (J. Dowding in litt. 2006). These and other observations indicate that the species may be in widespread decline (O'Donnell 1992, Maloney 1999, Taylor 2000, M. Szabo in litt. 2006).

New Zealand
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: In 2004, the New Zealand Department of Conservation estimated 1,000-5,000 mature individuals of this species (R. Hitchmough in litt. 2006), and a winter census in 2007 estimated c.5,000 individuals (per M. Bell in litt. 2012). Another estimate has put the total population at 7,000-10,000 individuals (R. Keedwell in litt. 2006), roughly equivalent to 4,600-6,700 mature individuals. Based on these estimates, the population is placed in the band for 2,500-9,999 mature individuals.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: It breeds on riverbeds, creating simple scrapes in the shingle. It usually lays two eggs. The young fledge after c.30 days. It feeds on freshwater invertebrates and small fish, taken as it forages over channels in gravelly rivers of South Island, occasionally taking earthworms and other invertebrates in terrestrial environments (on pastureland) and, when at sea, feeding mainly on crustaceans (Heather and Robertson 1997, O'Donnell and Hoare 2009). Adults in one colony fed their chicks 36-73 common skinks Oligosoma polychroma per hour (O'Donnell and Hoare 2009). 

Systems: Terrestrial; Freshwater; Marine

Threats [top]

Major Threat(s): Introduced mustelids Mustela spp., feral cats, brown rats Rattus norvegicus, hedgehogs, brush-tailed possums Trichosurus vulpecula, dogs, Australian Magpies Gymnorhina tibicen and other native bird species prey on this species (Taylor 2000, Keedwell et al. 2002, M. Bell in litt. 2012). Major breeding failures have been recently reported at colonies as a result of predation (G. A. Taylor in litt. 1999, Keedwell et al. 2002). Cattle and sheep can disturb breeding colonies. Recreational activities, presently increasing rapidly, can cause breeding failure and disturbance at wintering sites. Further hydroelectric developments are a major threat; notably an approved project on the Wairau River where 12% of the population currently nest (M. Szabo in litt. 2006). Invasion of introduced weed species and tree planting along riverbeds reduces available habitat (Taylor 2000) and forces birds to nest in areas more prone to flooding (M. Bell in litt. 2012). Confinement of rivers to a single channel reduces the availability of nesting "islands" (B. D. Bell verbally 1999). The species may be threatened at its roosting sites by predation, disturbance and development (M. Bell in litt. 2012).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
Several studies have been completed covering aspects of the species's biology and ecology. Habitat restoration and fauna monitoring is carried out by Project River Recovery in a number of major riverbed habitats in the McKenzie basin, covering part of the range (A. Grant in litt 1999, Taylor 2000). Some populations have received predator control measures with limited improvements to breeding success (M. Bell in litt. 2012).

Conservation Actions Proposed
Census and map all breeding colonies, and census winter flocks. Monitor accessible colonies annually. Examine all proposals for the development of hydroelectric dams or irrigation projects to identify impacts on the species. Establish nest protection if predation is identified as significantly affecting breeding success. Spray weeds on rivers if required (Taylor 2000), and commence a trial of establishing islands/rafts in lagoons and tarns (B. D. Bell verbally 1999).

Citation: BirdLife International 2012. Chlidonias albostriatus. The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 31 August 2015.
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