Species

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Justification
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.

Taxonomic source(s)
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Taxonomic note
The BirdLife Taxonomic Working Group is aware that phylogenetic analyses have been published which have proposed generic rearrangements which may affect this species, but prefers to wait until work by other taxonomists reveals how these changes affect the entire groups involved.

Synonym(s)
Chlidonias albostriatus Collar and Andrew (1988), Chlidonias albostriatus Collar et al. (1994), Chlidonias albostriatus Sibley and Monroe (1990, 1993), Chlidonias albostriatus albostriatus Collar and Andrew (1988), Chlidonias albostriatus albostriatus Collar et al. (1994), Chlidonias albostriatus albostriatus Sibley and Monroe (1990, 1993)

Identification
29 cm. Small, grey tern with black cap. Grey body and wings. Short, forked tail. White underparts. In flight, contrasting white rump. Bright orange legs, bill. Breeding adult, black cap extending to bill. Thin white line along cheek. Non-breeding adult, grey-flecked crown reduced to arc from eye to eye. Juvenile, similar except black-flecked crown, white chin. Similar spp. Whiskered Tern Chlidonias hybrida has even grey on rump. Little Tern S. albifrons has dark primaries on upper wings, yellow bill. Fairy Tern S. nereis has yellow-orange bill. White-fronted Tern S. striata, Common Tern S. hirundo are larger with black bill, legs. Voice Call repetitive kit.

Distribution and population
Sterna albostriata 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).

Population justification
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.

Trend justification
A very rapid population reduction is estimated on the basis of declines in breeding and wintering populations (O'Donnell 1992, Maloney 1999, Taylor 2000, R. Keedwell in litt. 2006, M. Szabo in litt. 2006).

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). 

Threats
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 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).

References
O'Donnell, C. F. J. 1992. Birdlife of the Ashburton River, Canterbury, New Zealand. Department of Conservation, Christchurch.

Heather, B. D.; Robertson, H. A. 1997. The field guide to the birds of New Zealand. Oxford University Press, Oxford, UK.

Maloney, R. F. 1999. Bird populations in nine braided rivers of the Upper Waitaki Basin, South Island, New Zealand: changes after 30 years. Notornis 46: 243-256.

Taylor, G. A. 2000. Action plan for seabird conservation in New Zealand. Department of Conservation, Wellington.

Keedwell, R. J.; Maloney, R. F.; Murray, D. P. 2002. Predator control for protecting kaki (Himantopus novaezelandiae) - lessons from 20 years of management. Biological Conservation 105: 369-374.

Further web sources of information
View photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Anderson, O., Benstead, P., Bird, J., Butchart, S., Calvert, R., Mahood, S., McClellan, R., Pilgrim, J., Taylor, J.

Contributors
Bell, B., Bell, M., Dowding, J., Grant, A., Hitchmough, R., Keedwell, R., Szabo, M., Taylor, G.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2013) Species factsheet: Sterna albostriata. Downloaded from http://www.birdlife.org on 23/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/05/2013.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

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