Data Zone
Taxonomic note
A. cygnoid (del Hoyo and Collar 2014) was previously listed as A. cygnoides but internal evidence does not justify this emendation (Dickinson and Remsen 2013). Sometimes placed in monospecific genus Cygnopsis. Monotypic.
Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
| Critically Endangered | Endangered | Vulnerable |
|---|---|---|
| - | A4bcd | A2bcd+4bcd |
| Year | Category | Criteria |
|---|---|---|
| 2023 | Endangered | A4bcd |
| 2016 | Vulnerable | A2bcd+3bcd+4bcd |
| 2013 | Vulnerable | A2bcd+3bcd+4cd |
| 2012 | Vulnerable | A2bcd+3bcd+4cd |
| 2008 | Vulnerable | A2b,c,d; A3b,c,d; A4b,c,d |
| 2006 | Endangered | |
| 2004 | Endangered | |
| 2000 | Endangered | |
| 1996 | Vulnerable | |
| 1994 | Vulnerable | |
| 1988 | Near Threatened |
| Migratory status | full migrant | Forest dependency | does not normally occur in forest |
| Land-mass type |
continent |
Average mass | - |
| Estimate | Data quality | |
|---|---|---|
| Extent of Occurrence (breeding/resident) | 3,940,000 km2 | medium |
| Extent of Occurrence (non-breeding) | 865,000 km2 | medium |
| Severely fragmented? | no | - |
| Estimate | Data quality | Derivation | Year of estimate | |
|---|---|---|---|---|
| Population size | 36000-43500 mature individuals | good | estimated | 2020 |
| Population trend | decreasing | poor | estimated | 2005-2033 |
| Rate of change over the past 10 years/3 generations (longer of the two periods) | 23-33% | - | - | - |
| Rate of change over the past & future 10 years/3 generations (longer of the two periods) | 50-60% | - | - | - |
| Generation length | 9.3 years | - | - | - |
| Number of subpopulations | 1-2,1 | - | - | - |
| Percentage of mature individuals in largest subpopulation | 100% | - | - | - |
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.
| Country/Territory | Presence | Origin | Resident | Breeding visitor | Non-breeding visitor | Passage migrant |
|---|---|---|---|---|---|---|
| China (mainland) | extant | native | yes | yes | yes | |
| Japan | extant | vagrant | yes | yes | ||
| Kazakhstan | extant | vagrant | yes | |||
| Mongolia | extant | native | yes | yes | ||
| North Korea | extant | native | yes | yes | ||
| Russia | extant | native | yes | yes | ||
| South Korea | extant | native | yes | yes | ||
| Turkmenistan | extant | vagrant | yes | |||
| Uzbekistan | extant | vagrant | yes |
| Habitat (level 1) | Habitat (level 2) | Importance | Occurrence |
|---|---|---|---|
| Artificial/Terrestrial | Arable Land | suitable | non-breeding |
| Grassland | Temperate | suitable | breeding |
| Marine Intertidal | Mud Flats and Salt Flats | major | non-breeding |
| Marine Neritic | Estuaries | major | non-breeding |
| Wetlands (inland) | Bogs, Marshes, Swamps, Fens, Peatlands | suitable | non-breeding |
| Wetlands (inland) | Permanent Freshwater Lakes (over 8ha) | major | non-breeding |
| Wetlands (inland) | Permanent Freshwater Lakes (over 8ha) | major | breeding |
| Wetlands (inland) | Permanent Freshwater Marshes/Pools (under 8ha) | major | non-breeding |
| Wetlands (inland) | Permanent Freshwater Marshes/Pools (under 8ha) | major | breeding |
| Wetlands (inland) | Permanent Rivers/Streams/Creeks (includes waterfalls) | major | non-breeding |
| Wetlands (inland) | Permanent Rivers/Streams/Creeks (includes waterfalls) | major | breeding |
| Altitude | 0 - 450 m | Occasional altitudinal limits |
| Threat (level 1) | Threat (level 2) | Impact and Stresses | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Agriculture & aquaculture | Annual & perennial non-timber crops - Agro-industry farming | Timing | Scope | Severity | Impact | ||||
| Ongoing | Majority (50-90%) | Rapid Declines | Medium Impact: 7 | ||||||
|
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| Agriculture & aquaculture | Livestock farming & ranching - Small-holder grazing, ranching or farming | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Agriculture & aquaculture | Marine & freshwater aquaculture - Industrial aquaculture | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Agriculture & aquaculture | Marine & freshwater aquaculture - Subsistence/artisinal aquaculture | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Biological resource use | Hunting & trapping terrestrial animals - Intentional use (species is the target) | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Climate change & severe weather | Droughts | Timing | Scope | Severity | Impact | ||||
| Ongoing | Whole (>90%) | Unknown | Unknown | ||||||
|
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| Climate change & severe weather | Habitat shifting & alteration | Timing | Scope | Severity | Impact | ||||
| Ongoing | Whole (>90%) | Unknown | Unknown | ||||||
|
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| Energy production & mining | Mining & quarrying | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Human intrusions & disturbance | Work & other activities | Timing | Scope | Severity | Impact | ||||
| Ongoing | Majority (50-90%) | Slow, Significant Declines | Medium Impact: 6 | ||||||
|
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| Invasive and other problematic species, genes & diseases | Viral/prion-induced diseases - Avian Influenza Virus (H5N1 subtype) | Timing | Scope | Severity | Impact | ||||
| Unknown | Majority (50-90%) | Unknown | Unknown | ||||||
|
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| Natural system modifications | Dams & water management/use - Large dams | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Natural system modifications | Fire & fire suppression - Increase in fire frequency/intensity | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Pollution | Industrial & military effluents - Type Unknown/Unrecorded | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Residential & commercial development | Commercial & industrial areas | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
|
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| Purpose | Scale |
|---|---|
| Food - human | subsistence, national |
Recommended citation
BirdLife International (2024) Species factsheet: Swan Goose Anser cygnoid. Downloaded from
https://datazone.birdlife.org/species/factsheet/swan-goose-anser-cygnoid on 23/12/2024.
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 23/12/2024.