LC
Common Gull-billed Tern Gelochelidon nilotica



Justification

Justification of Red List Category
This species has an extremely 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 is very large, and hence does not 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.

Population justification
The global population of G. nilotica and G. macrotarsa combined is estimated to number c.150,000-420,000 individuals (Delany and Scott 2006), but the global population of G. nilotica has not been estimated separately following the taxonomic split. The European population is estimated at 16,600-21,200 pairs, which equates to 33,200-42,400 mature individuals (BirdLife International 2015).

Trend justification
The population is suspected to be in decline owing to habitat loss and degradation in the core of its range (del Hoyo et al. 1996). The European population is estimated to be increasing (BirdLife International 2015).

Ecology

Behaviour The species breeds colonially in monospecific groups of 5-500 pairs (occasionally up to 1,000 pairs), or as solitary pairs amidst colonies of other species, remaining gregarious outside of the breeding season (del Hoyo et al. 1996, Snow and Perrins 1998). The northern populations of this species are migratory, dispersing widely after breeding before travelling southwards to the wintering grounds (del Hoyo et al. 1996).
 
Habitat Breeding It breeds in a variety of locations with bare or sparsely vegetated islands, banks, flats, or spits of dry mud and sand including barrier beaches (shoals), dunes, saltmarshes, saltpans, freshwater lagoons, estuaries, deltas, inland lakes, rivers, marshes and swamps (del Hoyo et al. 1996, Higgins and Davies 1996, Snow and Perrins 1998). During this season, it may also feed on emerging insects over lakes, agricultural fields, grasslands and even over semi-desert regions (del Hoyo et al. 1996). Non-breeding On passage the species typically forages over saltpans, coastal lagoons, mudflats, marshes and wet fields, overwintering on estuaries, saltpans, lagoons and saltmarshes, or in more inland sites such as large rivers, lakes, rice-fields, sewage ponds, reservoirs, saltpans and irrigation canals (del Hoyo et al. 1996, Higgins and Davies 1996, Snow and Perrins 1998). 

Diet It is an opportunistic feeder and is largely insectivorous taking adult and larval terrestrial and aquatic insects (such as Ephemeroptera, Odonata, Lepidoptera and Coleoptera) as well as spiders, earthworms, small reptiles, frogs, small fish (6-9 cm long), aquatic invertebrates and rarely voles and small birds (Richards 1990, del Hoyo et al. 1996). 

Breeding site The nest is a scrape in dried mud, sand or gravel on beaches, dry mudflats, dykes, sea-wrack on the tideline or on floating vegetation (Richards 1990, del Hoyo et al. 1996).

Threats

This species has been identified as particularly susceptible to abandonment of breeding sites due to human disturbance (Molina et al. 2014), although early dispersal from breeding sites appears to be a behavioural trait of the species that may mitigate the impact of disturbance.

Conservation actions

Conservation Actions Underway

CMS Appendix II. EU Birds Directive Annex I. Bern Convention Appendix II. A conservation scheme for the protection of gull and tern breeding colonies in coastal lagoons and deltas (e.g. Po Delta, Italy) involves protection from human disturbance, prevention of erosion of islet complexes, habitat maintenance and the creation of new islets for nest sites (Fasola and Canova 1996). The scheme particularly specifies that bare islets with 30-100 % cover of low vegetation (sward heights less than 20 cm) should be maintained or created as nesting sites (Fasola and Canova 1996).

Conservation Actions Proposed

The following information refers to the species's European range only: Identify important breeding areas for the species. Investigate the species's population ecology and potential threats and impacts, in order to inform conservation measures. Ensure the protection of breeding sites from disturbance, development and modification. Develop and implement suitable site management plans.

Acknowledgements

Text account compilers
Taylor, J., Everest, J., Symes, A., Malpas, L., Ashpole, J, Butchart, S., Calvert, R., Martin, R., Ekstrom, J., Stuart, A., Elliott, N.

Contributors
Evans, M.


Recommended citation
BirdLife International (2022) Species factsheet: Gelochelidon nilotica. Downloaded from http://www.birdlife.org on 11/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 11/08/2022.