This species is an uncommon visitor to southern Japan. These are adults showing all white plumage and yellow "spoons." Immatures are similar but have a pale bill and black wing-tips. This image shows non-reciprocal allopreening (the non-mutual preening of one individual exclusively by another of the same species, usually the mate or parent). This behavior has been documented in many bird species including the Eurasian Spoonbill (Harrison 1965). It is often initiated by the male and is thought to establish or maintain a pair bond. Two birds on the right are sleeping. Formerly this species was lumped with the Royal Spoonbill (P. regia) of Australia, but genetic studies have found that Royal's closest relative is the critically endangered Black-faced Spoonbill (P. minor) of East Asia. Canon PowerShot SX60.
Note: Plate 30 in the new "Birds of Japan" Helm field guide by Brazil seems to have the ages of the two flying birds reversed.
References:
Brazil, M. (2018) Birds of Japan, Helm.
Harrison, C.J.O. 1965. Allopreening as agonistic behaviour. Behaviour 24: 161-209.
Matheu, E., del Hoyo, J., Christie, D.A., Garcia, E.F.J., Kirwan, G.M. & Boesman, P. (2019). Eurasian Spoonbill (Platalea leucorodia). 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/52779 on 29 April 2019).