Data Zone
Justification of Red List category
This well-known species is listed as Endangered because of a suite of threats affecting it on the breeding and non-breeding grounds. In particular, on the breeding grounds it is impacted by disturbance and climate change induced droughts, and potentially other factors that render breeding productivity low. An increasing majority of this species' global population now winters at Poyang Lake, where birds are subject to a range of threats, including ongoing hydrological issues caused by the Three Gorges Dam, sand mining and climate change. Here, pollution is also believed to have had impacts on the species' ability to feed and the increasing congregation of birds here is a potential disease risk.
Population justification
A total population size of 54,400 wintering birds is estimated, following Damba et al. (2020). These are considered in two units: (1) 'Inland Flyway' and (2) 'Coastal Flyway' (nomenclature follows Damba et al. [2020], from which all estimated values herein are derived). The Inland Flyway unit winters in the Yangtze River floodplain, China, in which a total of 54,000 is estimated by averaging the total numbers counted on the Yangtze River in winters 2018/19 and 2019/20; this represents a significant reduction compared to the population estimate of 78,000 in 2000–2005 (Cao Lei et al. 2008). An increasing proportion (70-90%) of this population now winter at a single site: Poyang Lake. The Coastal Flyway population is significantly smaller, and may now be on the verge of extinction. Counts during winters 2015/16–2019/20 found only 368 in the Minjiang River estuary, and 47 in the Republic of Korea, leading Damba et al. (2020) to conclude this population comprised only 420 individuals, with no significant numbers (<5) wintering Japan in recent years. The proportion of mature individuals is unknown, but arbitrarily assuming a ratio of c.0.66–0.8 yields a total of 36,000–43,500.
Trend justification
Evidence of declines in this species since the 1940s/1950s are well documented from throughout its range (BirdLife International 2001, MNRE 2021, Wetlands International 2022).
Applying the data from Damba et al. (2020), a decline in the Yangtze River wintering population from 73,436 in 1987/88 to 51,791 in 2019/20, is extrapolated to an equivalent reduction of 21% over the three generations (c. 28 years: 1995–2023). However, there are two reasons this is likely to be an underestimate of the global trend: (1) the survey effort in 1978/1988 was substantially less expansive in scope than contemporary ones; and (2) the coastal flyway subpopulation (which winters elsewhere) has undergone a steeper decline over the same timeframe. Combining the trends of the two populations yields a decline of c. 23%, but attempting to account for differences in survey effort, the rate of reduction over the past three generations is estimated here to be 23–33%.
There is increasing evidence that this rate of decline may have now steepened, perhaps considerably. The number of birds in the Yangtze River floodplain and Jiangsu Province (>99% of global population) in 2004/2005 was estimated at 78,000, thus a count of c. 52,000 in 2019/2020 indicates a rate of decline equivalent to 53% over three generations. There is good reason to believe these data are representative, with the years chosen representing the first and most recent years in which synchronous waterbird surveys have been undertaken. Moreover, Damba et al. (2020) suggest that this is likely to be the minimum rate of reduction, since 'the Yangtze River floodplain survey coverage in 2018/19 and 2019/20 was extended to sites identified from satellite tracking data, which included more intensive survey of the centre of Poyang Lake'. Numbers wintering at Poyang Lake now account for 70–90% of the global population. Although the percentage of wintering birds at Poyang Lake is increasing (now accounting for 70–90% of the global population; see Table 4, Damba et al. 2020), even minor artefacts in survey effort could mask considerably steeper declines. Such recent rapid rates of decline are congruent with observations in Russia, although caution is noted on data from the latter given considerable natural inter-annual variation in response to climatic factors at individual sites. Nonetheless, MNRE (2021) report a rapid decline in some areas; e.g., a decline from 800 (early 2000s) to 400 in Khabarovsk, and in drought periods a near-total abandonment of Torey Lake for moulting (up to 2,300 in 2010, but none since 2018).
Determining future trends is difficult, but the key threats listed by Damba et al. (2020) show no sign of amelioration. Indeed, the number of threats could increase, especially if Poyang Lake continues to have fluctuating hydrology in response to the impacts of the Three Gorges Dam, sand mining and climate change (see Li et al. 2021 for review) or birds occurring there (at high density) are exposed to disease including HPAI. Similarly, climate change-induced droughts in Russia threaten breeding and moulting sites. Precautionarily therefore, the same rate of decline is suspected to occur over the next decade, thus between 2005 and 2033 the species is estimated to decline by 50-60%. Although there is little doubt that (without the mitigation of threats) this species will decline over the next three generations (2023–2041), there is too much uncertainty to accurately predict a rate.
The species occurs in two somewhat discrete flyways. Birds of the 'Inland Flyway' (sensu Damba et al. 2020) breed in Mongolia, the Durian steppe (Mongolia/Russia) and north-east China, extending east to Khanka Lake in eastern Russia. These birds mostly migrate south (on a broad front) through China, congregating at two lakes: Poyang and Shengjin. This flyway now makes up the majority (>99%) of the global population. A second, much smaller population ('Coastal Flyway' sensu Damba et al. 2020) breed at Udyl Lake and northern Sakhalin (eastern Russia) before migrating south, mostly to winter on the Minjiang River estuary in Fujian province, China. Some of this population remains in Korean Peninsula (North Korea and South Korea) in winter. The species historically wintered in Japan, but is now considered only a vagrant there. Birds have occasionally been recorded in Turkmenistan (Marochkina and Rustamov 2008) and birds have even bred in eastern Kazakhstan, but this is not thought to be regular. Away from here, escaped captive birds are reported globally (eBird 2023) and these can often be difficult to disentangle from genuine vagrants, especially in South-East Asia.
It breeds in wetlands in the steppe and forest-steppe zones, including river deltas, river valleys with meadows, the margins of brackish and freshwater lakes, and in mountainous areas along narrow, fast-flowing rivers. In winter, it occurs in lowland lakeside marshes, rice-fields, estuaries and tidal flats. Birds wintering at Shengjin Lake, China, have been observed feeding on below-ground tubers of Vallisneria asiatica and above-ground vegetation of sedges Carex spp. and canary grass Phalaris arundinacea (Fox et al. 2008). Recent research involving the satellite tagging of individuals has revealed that birds migrate in stages, stopping at a number of sites en route between breeding an wintering grounds (T. Mundkur in litt. 2006). Birds gather in large flocks to moult in late July prior to migration (O. Goroshko in litt. 2003).
Throughout this species' range, the loss and degradation of wetlands is the principal threat to it. Climate change, drought, land reclamation, grass-fires and anthropogenic disturbance are the key drivers of this. These problems have been described from the breeding and moulting regions in Mongolia, adjacent parts of Russia, and Inner Mongolia, China (e.g., Goroshko 2004, Choi et al. 2016, MNRE 2021). In China, the species is experiencing similar issues at staging sites in the north-east (Damba et al. 2020 and references therein) and the increasing reliance of Poyang Lake as a wintering site is of concern, especially given ongoing hydrological issues caused by the Three Gorges Dam, sand mining and climate change. Here, pollution is also believed to have had impacts on the species' ability to feed (Chen et al. 2019) and the increasing congregation of birds here is a potential disease risk, especially for avian influenza. Hunting was historically considered a substantial risk in China, although this has now abated somewhat. In Russia, the following threats have been identified: hunting, fires on breeding and moulting habitat, disturbance by people during nesting, changes in the hydrology of the Argun, disturbance by livestock during the nesting period (especially by cattle), pesticides, and predation by shepherd dogs. Many of these direct threats (particularly changes in fire regime and hydrology) and exacerbated by ongoing climate change (Goroshko 2004, Poyarkov 2005, MNRE 2021). On their own, each of these threats outlined is thought to be driving slow, significant declines, but combined they are estimated to be causing continuing declines that are very rapid.
Conservation Actions Underway
CMS Appendix II. It is legally protected in Russia, Mongolia and South Korea and some provinces in China. Several important sites are protected in Russia, Mongolia and China. Our understanding of the species' migration pattern has improved significantly following the deployment of satellite transmitters (see Damba et al. 2020 for summary, who call for these projects to be continued and expanded). The species is listed as Endangered at the national level in Russia (MNRE 2021).
Conservation Actions Proposed
Study its decline and establish more protected areas in its breeding grounds; determining the extent to which threats on the breeding ground are responsible for global population declines is important. Protect breeding and moulting habitats in Russia. Damba et al. (2020) call for a combined research and conservation effort that employs collaborations between Russia, Mongolia, China and South Korea, which are the key range states for the species. They suggest that their satellite monitoring work is continued and expanded to continue to identify key sites for the species, especially on migration. Given that the threats to this species are idiosyncratic at each site, there is an urgent need for coordinated and targeted conservation strategies, especially for the coastal flyway population, which may be at imminent risk of extinction. Throughout its range, but especially Russia where it is listed as a continuing key threat (MNRE 2021), the enforcement of hunting bans is essential. Given the importance of Poyang Lake, ameliorating the threats there (especially regarding sediment build up and hydrology) may be essential to this species' long-term conservation. Any outbreaks of HPAI need to be reported quickly and acted upon to avoid the spread through this congregatory species.
81-94 cm. Large goose with bi-colored neck and all black bill. Dark brown crown, nape and hindneck contrast strongly with pale creamy-brownish lower sides of head and foreneck. Adult has a whitish band from lores across forehead, bordering base of bill. Juvenile has duller crown, nape and hindneck and lacks whitish face-band. Similar spp. Greylag Goose A. anser has orange bill and lacks pale foreneck and whitish face-band. Voice Prolonged, resounding honk, ending at higher pitch. Repeated, short, harsh notes when alarmed.
Text account compilers
Berryman, A.
Contributors
Cao, L., Goroshko, O., Mundkur, T. & Peet, N.
Recommended citation
BirdLife International (2024) Species factsheet: Swan Goose Anser cygnoid. Downloaded from
https://datazone.birdlife.org/species/factsheet/swan-goose-anser-cygnoid on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.