Saunder’s gull (Larus saundersi)
|Also known as:||Chinese black-headed gull|
|Size||Length: 33 cm (2)|
Saunder’s gull is classified as Vulnerable (VU) on the IUCN Red List 2007 (1) and is listed on Appendices I and II of the Convention on Migratory Species (CMS or Bonn Convention) (3).
A small gull with a black hood and nape, but only during the breeding season, Saunder’s gull has a white body with pale grey wings and a narrow black tail band. The legs and short bill are black, and the body is squat. Non-breeding birds have a mottled grey hood and nape, and white-tipped wings with black markings on the primaries (2).
Breeding in eastern mainland China, as well as on the west coast of Korea, Saunder’s gull winters in eastern and southern China, Hong Kong, Macau, Taiwan, western and southern South Korea, southwestern Japan, and Vietnam. Non-breeders are found in North Korea (2).
It inhabits saltmarshes during the breeding season, nesting on the ground. During the winter it forages on estuarine tidal flats as well as drained aquaculture ponds nearby (2). It is mainly seen on coastlines, but some populations are found around inland wetlands (4).
Recognisable through its specialised feeding behaviour, Saunder’s gull flies over coastal mudflats 10 metres above the ground, searching for prey. On sighting a prey item it dives vertically, landing and pecking at the prey before it has time to enter its burrow. With this technique Saunder’s gull captures crabs and mudskippers, but during the winter it will also feed on fish and worms. It is known to steal prey from other bird species. The webbing on the feet on Saunder’s gull does not cover the whole foot, making this coastal species a poor swimmer. It appears to avoid water altogether, moving up the shore as the tide rises (4).
Saunder’s gull arrives at the breeding grounds in March and breeds from early April to early May. Monogamous pairs build a simple nest and defend their territory, attacking intruders. A clutch of two or three eggs is laid in May and is incubated for 21 to 23 days. Fledglings and adults leave the breeding grounds in October (4).
The reclamation of tidal flats and saltmarshes along coastlines of China, Taiwan, South Korea and Japan pose a serious threat to this coastal gull species. Already, key breeding sites have been abandoned following construction and development. Two breeding sites in China are heavily disturbed, as they are oilfields with an active extraction industry. Disturbance is a threat at many nest sites, particularly by lugworm collectors in China and photographers in South Korea, as disturbing adults results in increased predation of eggs and chicks (2).
Currently the key nesting sites in China are nature reserves and three wintering sites are protected areas, although this is poorly enforced. However, an important breeding colony at the Yellow River Delta Nature Reserve in China would benefit enormously from expansion to include further nest sites as well as the feeding sites of breeding birds. Sustainable coastal management plans are crucial for coastal species that are typically threatened by coastal development around the world. Saunder’s gull is not legally protected as yet (2).
For further information on the Saunder’s gull see:
- BirdLife International. (2001) Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK.
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- Colony: a group of organisms living together. Individuals in the group are not physiologically connected and may not be related, such as a colony of birds.
- Monogamous: having only one mate during a breeding season, or throughout the breeding life of a pair.
- Primaries: in birds, the outer flight feathers.
- Territory: area occupied and defended by an animal, a pair of animals or a colony.
IUCN Red List (November, 2011)