VU
Saunders's Gull Saundersilarus saundersi



Justification

Justification of Red List Category
This species's moderately small population is thought to be in decline. Over the next three generations (18 years), this decline is likely to become rapid as a result of land reclamation on tidal flats and disturbance at colonies, resulting in the species's listing as Vulnerable.

Population justification
A population estimate of 14,400 mature individuals has been derived from analysis of records and surveys by BirdLife International (2011). This is roughly equivalent to 21,000-22,000 individuals in total.

Trend justification
The species's population is presumed to be declining in line with the rate of habitat loss owing to land reclamation, which is anticipated to increase in the near future. Studies at specific sites have shown declines, for example a drop from over 900 individuals to 575 in the last 15 years at Yancheng National Nature Reserve (Jiang et al. 2010).

Distribution and population

Saundersilarus saundersi breeds in eastern mainland China, and sporadically at sites on the south-west coast of South Korea (BirdLife International 2001). The most important breeding grounds are Yancheng National Nature Reserve and Shuangtai Hekou National Nature Reserve in China. A count of 1,317 birds was made at Shuangtai Hekou, Liaoning, in October 2001 (Robson 2002), with 8,671 adults recorded and 399 banded in 2007 (Jiang 2007). At the Yellow River Delta of Shandong, 801 adults were recorded and 27 juveniles banded, while in Yancheng of Jiangsu, 575 adults were recorded in 2007 (Jiang 2007). Non-breeding birds occur in North Korea, where it may also breed. It winters in eastern and southern China (9,625 individuals), from Jiangsu southwards, Hong Kong (China) (35 individuals), Macau (China), Taiwan (China) (700 individuals), along the western and southern coast of South Korea (2,000 individuals), in south-western Japan (2,000 individuals) and in Vietnam (10 individuals) (Cao et al. 2008). The coast of Dandong is an important stopover site on the flyway of Panjing-Japan, with 232 adults sighted in April 2008, 75% of which were sub-adults in their first winter (Bai Quing-Quan 2008). The key wintering grounds are Bohai Bay, where 864 birds were counted in 2005/2006 (Liu Yang et al. 2007) and Wenzhou-Yueqing bays, Guangdong and Guangxi in China and Suncheon-Kwangyang bays, with c.750 individuals recorded at Kum River estuary in South Korea in January 2004 (K. Hark-Jin in litt. 2004). The global population is estimated to be 7,100-9,600 birds, although recent figures point to a minimum of 14,400 birds, mostly likely due to increased survey effort rather than any real increase in the population (Cao et al. 2008). However, it is likely that the population is continuing to decline, given the significant threats to habitat and high human disturbance levels occurring across the species's range (Jiang et al. 2010).

Ecology

The species nests on the ground and is restricted to common seepweed Suaeda glauca saltmarsh habitats. Wintering birds are found on estuarine tidal flats, with regular movements between different sites, dependent on weather and food supply.

Threats

The key threat facing this species is loss and degradation of the tidal flats and saltmarshes, and the subsequent loss of Common Seepweed Suaeda glauca, which is essential for breeding. In Yancheng National Nature Reserve, one of three breeding and wintering areas in China, the area of Common Seepweed reduced by 79% between 1992 and 2007, with the majority being replaced by aquaculture ponds (Jiang et al. 2010). Farmland area increased by 12% within Yancheng National Nature Reserve (Jiang et al. 2010), likely contributing to the loss of Common Seepweed. Further to this, there has been a continual increase in the ‘built-up’ area of Yancheng NNR in the period 1988-2006 (Ke et al. 2011), likely both for housing and commercial use. Reclamation developments associated with the Tianjin New Coastal District project, started in 2006, seriously impacted an important wintering area by autumn 2011, resulting in a substantial loss of inter-tidal mudflats in Tianjin municipality (P. Holt in litt. 2012). This conversion has occurred across much of the breeding range. Land use changes cause fragmentation of costal landscape and decreasing breeding habitat; changing water levels lead to losses of nests and chicks from rising water. There are no regulations to prevent the continued building of factories in Yancheng NNR (Jiang et al. 2010).

The introduced invasive Spartina alterniflora is displacing Common Seepweed in large swathes of habitat. The area of Yancheng NNR occupied by Spartina alterniflora increased by almost 400% between 1992 and 2007, over 90% of the increased area was mudflat prior to the growth  of  Spartina alterniflora (Jiang et al. 2010). The colonisation of mudflats by Spartina alterniflora causes sedimentation and constrains the natural transition of coastal vegetation, causing seepweed patches to thicken and become unsuitable for nesting (Liu et al. 2010). In 2010, only two patches of Suaeda glauca communities suitable for breeding remained in Yancheng NNR.

Egg collection represents a significant threat; major breeding site Shuangtai Hekou NNR supports 20,000 seasonal employees, known to collect eggs for food. Egg collection is also a problem in Yancheng NNR (Liu et al. 2009). Small-scale collection of bio resources, such as crabs, clamworm and seepweed, which disrupts incubation and causes desertion of breeding sites, increases risk of predation of chicks and eggs (Jiang et al. 2010) and has been recorded in Yancheng NNR and Shuangtai Hekou NNR.

The Yellow River Delta NNR, the third major breeding site for Saundersilarus saundersi in China, contains China’s second largest oilfield (The Diplomat 2016). This likely contributes to habitat loss and degradation, with the oil extraction activities thought to contribute to the high level of subsidence in the area (Zhang et al. 2015), as well as the disturbance of birds. Oil field exploration has been undertaken within Shuangtai Hekou National Park, with more than 100 drilling sites in 2002 (Kanai et al. 2002). There have not been any studies on the specific impacts to Saunders's Gull, however it does not seem to be causing significant decline in the population.

Conservation actions

Conservation Actions Underway
CMS Appendix I. The key nesting sites in China are all nature reserves. Wintering sites at Manko (Japan), Mai Po (Hong Kong), and Xuan Thuy (Vietnam) are all protected areas. The species is classed as Vulnerable in China and therefore receives full legal protection.

Conservation Actions Proposed
Conduct surveys in North Korea for potential breeding sites. Expand the Yellow River Delta Nature Reserve (China), to include additional nest-sites. Establish protected areas at the wintering sites of Wenzhou-Yueqing bays (China), Tutu estuary, Hanpao and Aoku (Taiwan (China)), Suncheon-Kwangyang bays (South Korea), Daijyu-garami, Hakata Bay and Sone (Japan). Provide management plans for coastal wetlands to promote their conservation and prevent the expansion of smooth cordgrass through active management measures (Jiang et al. 2010). Ensure full legal protection for this species.

Identification

33 cm. Diminutive gull with shortish, black bill. Breeding adults have black hood extending to nape and broad, broken white eye-ring. Non-breeders have white tips and small, black subterminal markings on outer primaries, small black tips to inner primaries, narrow, broken, dark secondary band and narrow black tail-band. Similar spp. Black-headed Gull Larus ridibundus is larger, less compact with longer bill and white leading edge to wing.

Acknowledgements

Text account compilers
Pilgrim, J., Stuart, A., Taylor, J., Anderson, O., Chan, S., Khwaja, N., Martin, R., Palmer-Newton, A., Benstead, P., Bird, J., Peet, N.

Contributors
Holt, P., Hark-Jin, K.


Recommended citation
BirdLife International (2022) Species factsheet: Saundersilarus saundersi. Downloaded from http://www.birdlife.org on 26/09/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/09/2022.