Migration routes of Tundra Swans satellite-tracked from northern Japan

Wenbo CHEN, Tomoko DOKO, Go FUJITA, Kan KONISHI, and Hiroyoshi HIGUCHI

Tundra Swans (Cygnus columbianus) breed in tundra regions near the North Pole, wintering in temperate regions of the coastal areas of the Pacific and Atlantic Oceans. The Eastern Palearctic (EP) flyway goes between southwest coast of Japan and the Arctic Ocean at the northeast region of Russia, passing through Hokkaido in Japan.

For the better understanding of the fall and spring migration of Tundra Swans, we captured 27 Tundra Swans during the winters of 2009 through 2012 (October to April) at Kutcharo Lake [EAAF053] near the town of Hamatonbetsu, Hokkaido to monitor their migration. There were 12 females and 8 males. The sexes of 7 individuals were unknown. All individuals were adults. The swans were captured using flat net traps or by hand. The swans were equipped with green neck collars to which satellite transmitters (platform transmitter terminals, PTTs; Figure 1) were attached. The PTTs used were solar-powered “SOLAR BIRDBORNE PTT” that weighed 12 g and were made by North Star Science and Technology LLC. A PTT and neck collar weighs approximately 47 g and is approximately 0.9% of the swan’s average body weight.

A Tundra Swan with a collar to which a platform transmitter terminal is attached. © Junko Nakajima

Tundra Swans’ migration can be classified into the wintering period, spring migration, breeding period, and autumn migration. Since individual swans do not leave a wintering site on the same day due to various conditions, e.g., microhabitats and/or microclimates, we developed an effective method to determine threshold dates of four migration status and named it the “MATCHED (Migratory Analytical Time Change Easy Detection) method”. Read the details here .

After applying the MATCHED method, the start date, end date, and duration for the wintering period, spring migration, breeding period, and autumn migration were calculated. Based on median values, wintering period began on 2 November and ended on 18 April; the spring migration began on 18 April and ended on 27 May; breeding period began on 28 May and ended on 9 September; and the autumn migration began on 9 September and ended on 2 November. The median durations for the wintering period, spring migration, breeding period, and autumn migration were 131 days, 48 days, 103 days, and 50 days, respectively. The start date and end date varied with the year. The mean ± SD duration at one stopover site for an individual was 5.5 ± 4.1 days and 6.8 ± 5.7 days for the spring and autumn migrations, respectively. The number of stopover sites was 3.0 ± 2.8 and 2.5 ± 1.2 for the spring and autumn migrations, respectively. The mean travel distance for the spring and autumn migrations were 6,471 km (SD = 1,879 km) and 6,331 km (SD = 604 km), respectively.

Seven routes were identified (Figure 2). The most common flyway was Route A which passed through Sakhalin. There were 15 wintering sites, 32 stopover sites, and eight breeding sites in total. All areas were related to water (rivers, lakes, lagoons, bays, and oceans), especially the mouth of Amur River, Udyl’ Lake (mouth of the Amur River), Shchastya Bay (mouth of the Amur River), Aniva Bay (southern Sakhalin), zaliv Chayvo Lake (northern Sakhalin), zal Piltun Lake (northern Sakhalin), zaliv Baykal Lake (northern Sakhalin), the Kolyma River, the Buyunda River (near the southern Kolyma River), Sen-kyuyel’ Lake (the Kolyma River), and the northern coastal areas of the Sea of Okhotsk.

There are various conservation issues for these areas, including habitat destruction and deterioration, collisions with wind turbines, chemical and radioactive pollutants, and hunting pressure. It is difficult to determine the impacts of these factors in each of the areas; however, these should be clarified in efforts to conserve the swans. Though the swans are not currently endangered, the above conservation issues are getting more and more serious and may cause drastic declines in swan populations in the near future.

Migration map of Tundra Swan

About the authors:
Wenbo Chen(1,2), Tomoko Doko(1,2), Go Fujita(3), Naoya Hijikata(1), Ken-ichi Tokita(4), Kiyoshi Uchida(5), Kan Konishi(6), Emiko Hiraoka(5) and Hiroyoshi Higuchi(1)

1 Keio Research Institute at SFC, Keio University, Japan
2 Nature & Science Consulting Co., Ltd., Japan
3 Laboratory of Biodiversity Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
4 lwate University, Japan
5 Satoyama Natural History Research Group, Japan
6 Hamatombetsu Lake Kutcharo Waterfowl Observatory, Japan

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