This Palearctic shorebird breeds in northern Japan but is primarily a migrant and winter visitor here in Southern Japan. It is a close relative of the Spotted Sandpiper (A. macularia) of North America and the two species were lumped in the past. The two are nearly identical in non-breeding (basic) plumage. However Common Sandpiper has a noticeably longer tail which projects well beyond the wing-tips as seen here. Its tail feathers also have more white fringing and its bill and legs are somewhat duller cf. Spotted Sandpiper. Both species are the only members of the genus Actitis; and both habitually teeter their rear ends up and down while foraging. Canon PowerShot SX60.
References:
Brazil, M. (1991) The Birds of Japan. Smithsoniun Inst. Press.
O'Brien, M, Crossley, R. & Karlson, K. (2006). The Shorebird Guide. Houghton Mifflin.
Van Gils, J., Wiersma, P. & Kirwan, G.M. (2019). Common Sandpiper (Actitis hypoleucos). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53912 on 7 May 2019).