Dr Nial Moores, National Director, Birds Korea, January 28th 2025
Media reports identify the bird species involved in the deadly Muan air-crash in the southwest of the Republic of Korea on December 29th 2024 as Baikal Teal Sibirionetta formosa 가창오리, with blood and feathers found in both engines. It therefore appears that the plane collided with a flock of this species. This post aims to provide some basic information on Baikal Teal, to help media and airport investigators (and decision-makers) to interpret this information.
The Baikal Teal (scientific name Sibirionetta formosa, formerly Anas formosa) is a fairly small species of duck, with a total length of 39-43 cm (Carboneras & Kirwin 2020) and a mass of 402-505 g (Moores in Kear 2005).
Breeding in Russia, the Baikal Teal is well-known for forming spectacular, densely-packed single-species concentrations in wintering areas in the Republic of Korea (ROK), and to a lesser extent in Japan and PR China. These wintering areas are occupied between October / November and March.
Some Baikal Teal flocks in December and January contain several hundred thousand individuals, comprising most of the world population, currently estimated at 500,000-700,000 individuals (Wetlands International 2025).
Once a species of natural, extensive floodplain habitats, nowadays the main habitat in winter of Baikal Teal is large lakes surrounded by rice-fields as are typically found in large-scale reclamation areas (i.e., areas converted from natural wetland to artificial wetland and land through mechanical means). This is because Baikal Teal feed largely on spilt rice-grains in rice-fields (picked up by birds walking, “grazing”), and prefer to roost in dense flocks out on open, non-flowing water, at a safe distance from predators.
Once in such habitat, the Baikal Teal:
“Roosts in dense, effectively single-species concentrations during day and flies in shorebird-like clouds to feed on spilt rice and grain in late evening and night (Allport et al. 1991). Evening flights often involve elaborate “aerial ballet” with swirling flocks…Although flock usually leaves roost as a single unit, this breaks into smaller groups rapidly. Many return to daytime roost before first light; almost all before sunrise…When roosting largely inactive until mid-afternoon, unless disturbed” (Moores in Kear 2005).
Evening flight of Baikal Teal, Lower Geum River, January 2024 © Nial Moores. Distant flocks often look like – and could perhaps be mistaken by pilots – as thin grey clouds
As Baikal Teal roost during the day important questions for people investigating this accident include:
- Why was this flock of Baikal Teal flying high enough to collide with this aircraft on approach more than an hour after sunrise?
- What disturbed them?
- Where were they roosting?
- And in consideration of guidance provided by the International Civilian Aviation Organisation, if roosting within 8km or 13km of the airport, was the Wildlife Hazard Management Program adequate?
In the ROK, habitat used by Baikal Teal is very often shared with Greater White-fronted Geese Anser albifrons 쇠기러기 and Tundra Bean Geese Anser serrirostris 큰기러기. Because of their flocking behaviour, these species also potentially pose a high bird strike risk at airports built in areas close to reclamation lakes and rice-fields, as in Muan (and as proposed on Baengnyeong Island, in Hwaseong, in Seosan and at Saemangeum).
The winter bird census, conducted under the auspices of the National Institute of Biological Resources within the National Ministry of Environment, covers approximately 200 of the more important known waterbird sites in the ROK.
In January 2024 (the most recent Winter Census data that are available), no Baikal Teal were recorded using the Muan Reservoir. However, there were 1,157 Bean Geese and 412 Greater White-fronted Geese in and around the reservoir (NIBR 2024).
In addition, in January 2021, 35,000 Baikal Teal were recorded by the winter census along the Muan-Mokpo coast, to the south of the Muan International airport (i.e., on the flight approach of aircraft landing on “Runway 1”) (NIBR 2018-2023).
The winter census is not conducted with enough frequency to build a robust understanding of waterbird usage at each site; or of movements between them. Moreover, in winter, the Baikal Teal is largely “nomadic” (Moores in Kear 2005). In addition to spreading out up to 30km each night (Tajiri et al. 2014), Baikal Teal often move much larger distances in response to e.g., the freezing over of lakes that they roost on, or snow cover which prevents them from feeding. As a result, numbers fluctuate almost daily even at often-preferred sites, like the lower Geum River (Yu et al. 2014) near the proposed Saemangeum New Airport.
Increases in Waterbirds mean increasing Bird Strike Risk?
Some materials published by the International Civilian Aviation Organisation, occasionally repeated in the ROK, suggest that bird strike is increasing around the world and in the ROK because of the increasing success of conservation measures for waterbirds. Although this might be true of some parts of the world, data from the winter census do not lend strong support to this assertion in the ROK (Table 1), especially when potential biases in the data are considered (e.g., increasing experience of observers; better equipment; and increased number of sites compared with earlier years).
Table 1. Counts of birds made during five recent winters of the National Bird Census, with counts of selected waterbird species considered by Birds Korea to pose the highest bird strike risk to aircraft in winter months.
2018-2019 | 2019-2020 | 2020-2021 | 2021-2022 | 2022-2023 | |
Grand Total | 1,469,383 | 1,628,873 | 1,445,528 | 1,745,723 | 1,689,084 |
Geese, Swans and ducks | 1,045,232 | 1,135,882 | 940,569 | 1,210,730 | 1,100,233 |
Baikal Teal | 355,116 | 406,351 | 304,521 | 435,962 | 420,824 |
Greater White-fronted Goose | 178,326 | 182,608 | 117,670 | 139,859 | 127,843 |
Tundra Bean Goose | 108,840 | 87,881 | 83,316 | 108,258 | 103,017 |
Great Cormorant | 17,634 | 23,088 | 25,809 | 38,832 | 28,093 |
It is true that the Baikal Teal is much more numerous now than 50 years ago, when the species was threatened with extinction due to e.g., habitat loss and then over-hunting. However, the peak number of Baikal Teal recorded during the winter census reached over a million in January 2009, but has remained below 600,000 in all winters since 2011.
The most recent published national winter census counts were 335,610 and 362,531 in December 2023 and January 2024 respectively (NIBR 2024), with the latter count representing 24.1% of all birds recorded that census. Based on these data, the Baikal Teal remains the commonest duck species in winter in the ROK and the commonest bird recorded during the census.
The number of bird strike incidents in the ROK is therefore not increasing because of an increasing number of waterbirds. It is increasing because of the increasing number of flights. And it is reasonable to assert that the highest risk of bird strike in winter is likely to be at airports where the largest numbers of waterbirds are known to concentrate.
A review of aviation safety in the ROK therefore needs to include a much more serious consideration of the bird strike risk. In turn, this requires a full reassessment of several proposed airports in reclamation areas and near wetlands (e.g., on Baaengnyeong Island, in Hwaseong, in Seosan, in Saemangeum, in Busan and on Jeju) as well as at Muan.
Please also see:
“Safety First? Building Airports in Wetlands and next to Migratory Bottlenecks” (January 6th 2025)
“Winter Bird Census Counts within 13km of Muan International Airport” (December 30th 2024)
“A Global Perspective: Why is the high risk of bird strike at the proposed Gadeokdo airport still being overlooked?” (August 2024)
“Recent Cancellation of a Proposed New International Airport next to an estuary in Portugal: something for us to learn from!” (June 2024)
“Proposed air base relocation to the Hwaseong Wetlands would be ecologically disastrous” (August 2022)
References
Carboneras, C. and G. M. Kirwan. 2020. Baikal Teal (Sibirionetta formosa), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.baitea.01
Moores, N. 1996. The Baikal Teal in South Korea. Hong Kong Bird Report 1995:231-35. Published in 1996.
Moores, N. 2005. Baikal Teal. (pp. 605-608 in Keir [ed.] Ducks, Geese and Swans. Volume 2, published by Oxford University Press.
National Institute of Biological Resources (NIBR). 2018-2023. National Winter Census, conducted under the auspices of the Ministry of Environment. NIBR, Incheon, Republic of Korea. (in Korean: 겨울철 조류 동시 센서스 2008-2023. 국립생물자원관: 대한민국 인천.). Accessed through database built by Andreas Kim at: https://www.andreas-kim.de/MoE/MoE-Winterbird-Censuses-Species-V2.html
NIBR. 2024. 2023-2024 Winter Waterbird Census of Korea. Conducted under the auspices of the Ministry of Environment. NIBR, Incheon, Republic of Korea. Accesed in January 2025 at: https://species.nibr.go.kr/board/viewPost.do?boardNo=249&artNo=35942&vmode=V
Tajiri H., Sakurai Y., Tagome K et al. 2014. Satellite telemetry tracking of Baikal Teals (Anas formosa) in annual migration wintering in Katano-Kamoike, Central Japan. Pages 311- 316. In Proceedings of the International Conference on Distribution, Migration and Other Movements of Wildlife, Vladivostok, 25–27 November 2014.
Wetlands International. 2025. Waterbirds Populations Portal. Accessed in January 2025 at: https://wpe.wetlands.org/
Yu J-P., Han S-W., Paik I-H. et al. 2014. Status of wintering populations of the baikal teal (Anas formosa) in Geumgang River, Korea. Journal of Asia-Pacific Biodiversity. Vol 7., Issue 2, Pages e213-e217. (at: https://www.sciencedirect.com/science/article/pii/S2287884X14000211)