This distinctive large dark race is sometimes split under the name Owston's Woodpecker (D. owstoni) or Amami Woodpecker. In fact it looks quite different from other populations of White-backed Woodpecker in being much larger, darker and lacking the obvious white lower back. It is endemic to the Island of Amami -Oshima where it is uncommon. It specializes in old mature forest mainly on the hilltops where it is threatened by habitat loss. IUCN classifies it as "near threatened" with a total population of under 2500. Japan classifies it as a "National Treasure." Canon PowerShot SX60 HS.
References:
Brazil, M. (1991). The Birds of Japan. Smithsonian Inst. Press.
Brazil, M. 2018. Birds of Japan. Helm.
BirdLife International 2016. Dendrocopos owstoni. The IUCN Red List of Threatened Species 2016: e.T22727132A94941890. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22727132A94941890.en. Downloaded on 04 October 2019.
del Hoyo, J., Collar, N. & Christie, D.A. (2019). Amami Woodpecker (Dendrocopos owstoni). 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/467493 on 4 October 2019).
Winkler, H., Christie, D.A. & Nurney, D. (1995) Woodpeckers: An Identification Guide to Woodpeckers of the World. Houghton Mifflin.