LC
Saunders's Tern Sternula saundersi



Justification

Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Trend justification
The population is suspected to be in decline owing to disturbance and predation at breeding sites (del Hoyo et al. 1996).

Distribution and population

This poorly known species breeds along the coasts of the Red Sea south to Socotra (Yemen) and Somalia, and around the Persian Gulf off Saudi Arabia, Iran and Oman, to north-west India, Sri Lanka, Adu Atoll (Maldives), and possibly the Amirantes Islands of the Seychelles (del Hoyo et al. 1996). North-east African birds move south as far as Tanzania in winter, and birds around the Red Sea also move south within the breeding range. Birds in south-east Somalia, Sudan and Socotra are resident. Other populations appear to migrate eastwards to the west coast of India, Sri Lanka, Laccadives (to India) and Maldives, Seychelles and Malaysia (Snow and Perrins 1998). The location of its breeding colonies is mostly unknown. In Iran, c.150 pairs nested in seven colonies in the 1970s, a small population was known to breed in Bahrain which appeared to decrease substantially from 1969-1971 to 1981, and 29+ pairs bred in 1983 on the Farasan Archipelago in Saudi Arabia (Gallagher et al. 1984).

Ecology

The movements of this species are not well known, although many individuals winter outside of their breeding range (del Hoyo et al. 1996). The species breeds in solitary pairs or small loose colonies of 5-30 pairs (Gallagher et al. 1984, del Hoyo et al. 1996, Snow and Perrins 1998). It inhabits shallow tropical and subtropical inshore waters, estuaries, tidal lagoons and harbours, often feeding up to 15 km offshore and nesting up to 2 km inland (del Hoyo et al. 1996, Snow and Perrins 1998). Diet consists of small fish, crustaceans, molluscs and insects (del Hoyo et al. 1996). The nest is a hollow (e.g. an animal footprint) in bare sand, shingle or dried mud just above the high tide line on beaches, on mudflats or up to 2 km inland (del Hoyo et al. 1996, Snow and Perrins 1998). It shows a preference for nesting on small mounds of wind-blown sand surrounding plants or other objects, and in breeding colonies neighbouring nests are usually placed between 20 and 100 m apart (del Hoyo et al. 1996).

Threats

The species is considered to suffer from many of the same threats as the closely related Little Tern, Sternula albifrons (Gochfeld et al. 2018), including disturbance from birdwatchers, photographers and the gereral public; egg collection; and loss of beach nesting habitat to sea-level rise.

Acknowledgements

Text account compilers
Stuart, A., Ekstrom, J., Butchart, S., Harding, M., Malpas, L., Martin, R.


Recommended citation
BirdLife International (2021) Species factsheet: Sternula saundersi. Downloaded from http://www.birdlife.org on 09/03/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 09/03/2021.