Species

Justification
This species is listed as Near Threatened owing to its moderately small population. If this is found to be undergoing a decline, the species may qualify for uplisting to a higher threat category.

Taxonomic source(s)
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

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.

Identification
23 cm. Small, very pale tern. Adult has black cap extending onto nape and very pale grey back. In flight, black triangular wing tip runs from the carpal to primary tip. Non-breeding adult shows white forehead and crown, with black mask extending and joining on nape. Immature has buff barring on mantle. Similar spp. Breeding Little Tern Sterna albifrons has white forehead and mainly yellow bill. In non-breeding, has less white on head, darker mantle and more slight proportions. Voice Sharp, high-pitched tsit tsit and harsh, rapid kid-ick.

Distribution and population
Sterna balaenarum is recorded in the breeding season along the coast of Namibia (98% of the population nest between the Orange and Cunene rivers [Braby et al. 2001]), south to the Cape provinces in South Africa (less than 125 pairs [Braby et al. 2001]) and north to Cabinda in Angola (Gochfeld and Burger 1996), where there are less than 190 pairs (Simmons 2010). A recent survey between Tombua and the Cunene River mouth (197 km) recorded 573 individuals, with a breeding colony (6 pairs) located 30 km north of the Cunene River (Simmons 2010). It disperses north after the breeding season and is recorded regularly from the coastal waters of Democratic Republic of Congo, Congo, Gabon, Cameroon, Nigeria, Benin, Togo, Ghana and Côte d'Ivoire (Urban et al. 1986, Demey and Fishpool 1991, Gochfeld and Burger 1996). During 2002, the total population was estimated at 14,000 birds (Simmons et al. 1998b, du Toit et al. 2002), with peak density in the central area of its range (around 23°S) - apparently the main spawning ground of many fish species - and decreasing density north and south along Namibia's 1,470 km coast (Simmons et al. 1998b).

Population justification
The population is estimated at 14,000 individuals, roughly equivalent to 9,300 mature individuals.

Trend justification
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.

Ecology
Behaviour This species is a partial migrant (Urban et al. 1986). It breeds between late October and mid-November (del Hoyo et al. 1996) in small groups usually consisting of 4-10 pairs, although occasionally of up to 60 (Urban et al. 1986, del Hoyo et al. 1996). Pre-migratory flocks of tens, hundreds or occasionally thousands of birds gather at the Namibian coast in April (Hockey et al. 2005), and then move northwards as far as Nigeria and Ghana (del Hoyo et al. 1996, Hockey et al. 2005). The species is most numerous here between July and October (del Hoyo et al. 1996), coinciding with the arrival of strong upwellings off the Ghanaian coast which bring spawning fish inshore (Hockey et al. 2005). About 100 individuals remain in the breeding grounds year-round. Outside the breeding season it roosts colonially (Urban et al. 1986) but usually feeds solitarily, with individuals spaced 10-50m apart (Urban et al. 1986). It returns to its breeding grounds in September and October (Hockey et al. 2005). Habitat This species is predominantly coastal (Hockey et al. 2005). Breeding On gravel and stony plains, salt pans and dunes (Urban et al. 1986, del Hoyo et al. 1996, Hockey et al. 2005), sometimes in sheltered bays and shallow reefs (Hockey et al. 2005), but often several kilometres inland (del Hoyo et al. 1996). Recently breeding has been observed up to 11.5 km from the coast in southern Namibia (Braby et al. 2001). It will also breed on rocky ledges and at rehabilitated diamond mines, favouring breeding localities that provide good visibility (Harrison et al. 1997a). It shuns outer beach areas that are frequented by predators (Gochfeld and Burger 1996, del Hoyo et al. 1996). There are very few records of breeding on islands (Hockey et al. 2005). Non-breeding During the non-breeding season it is found on more exposed, high-energy coasts (Hockey et al. 2005). The species usually feeds in the shallow, inshore waters of bays, estuaries, lagoons and salt-pans and in the surf zone (Urban et al. 1986, Gochfeld and Burger 1996, del Hoyo et al. 1996), but occasionally forages in the open ocean, as far as 5km from land (Hockey et al. 2005). Diet It feeds mainly on small fish (usually less than 50mm in length [Hockey et al. 2005]), including mullet Mugil richardsonii and anchovy Engraulis japonica, as well as small squid (del Hoyo et al. 1996). Breeding site Eggs are laid in a nondescript scrape (del Hoyo et al. 1996), sometimes lined with shell chips or small stones (Hockey et al. 2005). The clutch-size is usually one, rarely two, and the incubation period is 18-22 days, followed by a fledging period of 20 days and 2.5 months of dependency (del Hoyo et al. 1996).

Threats
Land claim, dredging and hotel construction threaten some feeding areas; off-road vehicles may destroy nests (but are not a threat to whole breeding colonies as this species does not desert colonies like other terns [Demey and Fishpool 1991]) particularly as the breeding season coincides with peak human activity on beaches in summer (Gochfeld and Burger 1996). The largest breeding colony known (minimum of 120 pairs [Braby et al. 2001]), Caution Reef, south of Swakopmund, is on town land and suffers considerable human disturbance (Cheke and Walsh 1996). Large-scale mining operations have caused disturbance both to offshore feeding and onshore breeding areas (Simmons et al. 1998b), resulting in a drop from 20 breeding pairs to 2-7 pairs at Elizabeth Bay between 1996 and 2002 (Simmons 2005). However, diamond mining is due to end in the next five years and tern populations may then increase again (R. E. Simmons in litt. 1999, Braby et al. 2001). Some roosting birds are caught in snares by children on the wintering grounds (Cheke and Walsh 1996).

Conservation actions underway
CMS Appendix II. In November 2000, information boards and barriers were used to successfully prevent off-road vehicles entering the breeding site at Caution Reef. This resulted in a slightly increased nesting density and enabled hatching success to increase from 56% to 80% (Braby et al. 2001).

Conservation actions proposed
Monitor population trends. Designate disturbance-free areas on nesting beaches. Protect important breeding sites.

Related state of the world's birds case studies

• Uranium Mining and Important Bird Areas in Namibia: a need for strategic environmental assessment
• Business needs to take biodiversity on board

References
Urban, E. K.; Fry, C. H.; Keith, S. 1986. The birds of Africa vol. II. Academic Press, London.

Gochfeld, M.; Burger, J. 1996. Sternidae (Terns). In: del Hoyo, J.; Elliott, A.; Sargatal, J. (ed.), Handbook of the birds of the world, pp. 624-667. Lynx Edicions, Barcelona, Spain.

Demey, R.; Fishpool, L. D. C. 1991. Additions and annotations to the avifauna of Côte d'Ivoire. Malimbus 12: 61-86.

del Hoyo, J.; Elliott, A.; Sargatal, J. 1996. Handbook of the Birds of the World, vol. 3: Hoatzin to Auks. Lynx Edicions, Barcelona, Spain.

Cheke, R. A.; Walsh, J. F. 1996. The birds of Togo: an annotated checklist. British Ornithologists' Union, Tring, U.K.

Harrison, J. A.; Allan, D. G.; Underhill, L. G.; Herremans, M.; Tree, A. J.; Parker, V.; Brown, C. J. 1997. The atlas of southern African birds. BirdLife South Africa, Johannesburg.

Simmons, R. E.; Cordes, I.; Braby, R. 1998. Latitudinal trends, population size and habitat preferences of the Damara Tern Sterna balaenarum on Namibia's desert coast. Ibis 140: 439-445.

Braby, R. J.; Shapira, A.; Simmons, R. E. 2001. Successful conservation measures and new breeding records for Damara Terns Sterna balaenarum in Namibia. Marine Ornithology 29: 81-84.

Du Toit, M.; Boere, G. C.; Cooper, J.; de Villiers, M. S.; Kemper, J.; Lenton, B.; Petersen, S. L.; Simmons, R. E.; Whittington, P. A.; Byers, O. P. 2002. Conservation assessment and management plan for southern African seabirds.

Simmons, R.E. 2005. Reviewing the conservation status of the Black Harrier, Circus maurus. Gabar 16: 29-31.

Hockey, P. A. R.; Dean, W. R. J.; Ryan, P. G. 2005. Roberts birds of southern Africa. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa.

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., Butchart, S., O'Brien, A., Pilgrim, J., Shutes, S., Taylor, J.

Contributors
Simmons, R.

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

Recommended citation
BirdLife International (2013) Species factsheet: Sterna balaenarum. Downloaded from http://www.birdlife.org on 21/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/05/2013.

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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