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Additional file 2: Figure S1. Eurasian Spoonbill ES06 migration route map. Figure S2. Eurasian Spoonbill ES07 migration route map. Figure S3. Eurasian Spoonbill ES08 migration route map.

Until recently, almost nothing was known about the migration routes, flyway structure and population status of the Mute Swan Cygnus olor in East Asia. Here, we use a combination of GPS telemetry data, collar resightings, published literature and expert advice to update existing knowledge of its summer and winter distribution in the region, and to provide a preliminary description of the swans’ migration and habitat use. Three flyway units were indicated for the Mute Swan in East Asia. The Eastern China-wintering unit includes swans summering along the lower Selenga River in Russia, in central Mongolia and Inner Mongolia in China, which winter on the coast of eastern China, where 403 swans were counted in 2014/15, but where less than 30 have been counted in very recent years. In the absence of better data, we conservatively estimate this Chinese-wintering group at 400 birds. Mute Swans in the Korean-wintering unit are individuals that winter along the Korean Peninsula and summer in Inner Mongolia (China) and the Amur region (on the border of China and Russia); they are poorly covered by the mid-winter waterbird counts in South Korea and we have no knowledge of numbers wintering in North Korea. Finally, mid-winter counts of the introduced and sedentary population of Mute Swans in Japan have amounted to c. 240 birds in the last five years. We therefore suspect that there are likely c. 1,000 Mute Swans in Far East Asia, but await improved coverage throughout the entire wintering grounds to provide a better population estimate, with the species confirmed as one of the poorer known of the migratory waterbirds in the region. A single GPS-tagged Mute Swan tracked successfully provided detailed information on its migration routes, timing of migration and habitat use (almost exclusively waterbodies) over four complete migration episodes. It summered at Dalai Lake, China, used three stopover sites (on the borders of Russia and North Korea, in North Korea, and Baicheng City in China) during spring and autumn migration, and showed site fidelity to summer, winter and stopover sites. Combined count data and GPS data suggested that Mute Swans mostly occur within protected areas throughout the year. However, further research is required to establish the true distribution and abundance of this small and scattered species within these three flyways in East Asia, as well as to confirm its population structure and migration routes.

European populations of the Greylag Goose Anser anser have been studies for over 50 years, but those in the East Asian flyway are less well known. Here we describe the breeding and wintering distribution of Greylag Geese wintering in China, based on historical and newly-reported telemetry data (from 31 individuals contributing complete migrations), wintering waterbird surveys and expert knowledge. Historical records, and also the data presented here, indicate that Greylag Geese breeding in the north of the Xinjiang Uygur Autonomous Region, China, and in Mongolia east of 93°E, through Inner Mongolia to western parts of Heilongjiang Province, China, likely almost all winter east of 107°E in China (97% in the Yangtze River floodplain and 3% in the Yellow River floodplain). Annual mid-winter waterbird counts confirm that very few Greylag Geese winter in Japan and South Korea. Count data suggest that the Far East Asia Greylag population wintering in China currently numbers 30,000 individuals, a major increase compared to 3,263 counted in 2005. Historical records however indicate that the wintering distribution was far greater 30 years ago, and that Greylag Geese are now less common than previously in Guangdong, Guizhou, Hainan, Henan, Hunan, Anhui and Jiangsu Provinces, as the species has become more concentrated further north in the Yangtze and Yellow River floodplains. On the basis of count data from winters 2010/11–2019/20, we identified 21 current key wintering sites (holding ≥ 1% of the flyway population, i.e. 300 birds) in the Yangtze River floodplain and one in the Yellow River floodplain for this population. Increasing use of farmland in winter, as well as site protection and sympathetic local management of wintering sites may have contributed to recent increases in Greylag Goose abundance in the flyway. These results provide a more robust basis for assessing the current status of the Far East Asia Greylag Goose population and a guide to priorities for further internationally coordinated research of the species. The need to improve monitoring and habitat management for maintaining the increasing numbers wintering in China is also emphasiseduropean populations of the Greylag Goose Anser anser have been studies for over 50 years, but those in the East Asian flyway are less well known. Here we describe the breeding and wintering distribution of Greylag Geese wintering in China, based on historical and newly-reported telemetry data (from 31 individuals contributing complete migrations), wintering waterbird surveys and expert knowledge. Historical records, and also the data presented here, indicate that Greylag Geese breeding in the north of the Xinjiang Uygur Autonomous Region, China, and in Mongolia east of 93°E, through Inner Mongolia to western parts of Heilongjiang Province, China, likely almost all winter east of 107°E in China (97% in the Yangtze River floodplain and 3% in the Yellow River floodplain). Annual mid-winter waterbird counts confirm that very few Greylag Geese winter in Japan and South Korea. Count data suggest that the Far East Asia Greylag population wintering in China currently numbers 30,000 individuals, a major increase compared to 3,263 counted in 2005. Historical records however indicate that the wintering distribution was far greater 30 years ago, and that Greylag Geese are now less common than previously in Guangdong, Guizhou, Hainan, Henan, Hunan, Anhui and Jiangsu Provinces, as the species has become more concentrated further north in the Yangtze and Yellow River floodplains. On the basis of count data from winters 2010/11–2019/20, we identified 21 current key wintering sites (holding ≥ 1% of the flyway population, i.e. 300 birds) in the Yangtze River floodplain and one in the Yellow River floodplain for this population. Increasing use of farmland in winter, as well as site protection and sympathetic local management of wintering sites may have contributed to recent increases in Greylag Goose abundance in the flyway. These results provide a more robust basis for assessing the current status of the Far East Asia Greylag Goose population and a guide to priorities for further internationally coordinated research of the species. The need to improve monitoring and habitat management for maintaining the increasing numbers wintering in China is also emphasised.