This species is primarily a winter visitor to Japan. Rustic Bunting is now listed as "vulnerable" by IUCN because of recent steep declines attributed to extensive trapping in China. This activity decimated the Yellow-breasted Bunting population which has declined by an estimated 95%. Similar recent steep declines have been noted in the Rustic Bunting.
The asymmetric dark bases to the tertials are diagnostic of Emberiza buntings. Although the rusty nape and rump are diagnostic, the pale spot at the rear of the ear coverts and white wing bars are characters useful in separating Rustic Bunting from Reed Bunting which has buffy wing bars in Fall and Winter. The rectrix tips are not strongly pointed suggesting this is an adult (AHY) bird. The black on the crown and ear coverts suggests this is a probably a winter plumage male. In females these areas are usually brown.
Two subspecies are recognized. Nominate E. r. rustica ranges across northern Eurasia east to Central Siberia. It is replaced by E. r. latifascia in the Russian Far East to Kamchatka. All Japanese specimens are attributed to latifascia which has a blacker crown and broader ventral streaks, but differences are slight and the two subspecies probably not distinguishable in winter plumage. IOC and H&M4 consider the species to be monotypic.
Canon PowerShot SX60.
References:
Bird Banding Manual - Identification Guide to Japanese Birds (1982).
BirdLife International 2016. Emberiza rustica. The IUCN Red List of Threatened Species 2016: e.T22720960A89641304. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22720960A89641304.en. Downloaded on 25 April 2019.
Brazil, M.A. (1991) The Birds of Japan. Smithsonian Inst. Press.
Byers, C., J. Curson, and U. Olsson. (1995) Sparrows and Buntings: A Guide to the Sparrows and Buntings of North America and the World. Houghton Mifflin, Boston.
Copete, J.L., Garcia, E.F.J. & Sharpe, C.J. (2019). Rustic Bunting (Emberiza rustica). 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/61884 on 25 April 2019).
Edenius, Lars & Choi, Chang-Yong & Heim, Wieland & Jaakkonen, Tuomo & de Jong, Adriaan & Ozaki, Kiyoaki & Roberge, Jean-Michel. (2016). The next common and widespread bunting to go? Global population decline in the Rustic Bunting Emberiza rustica. Bird Conservation International. -1. 1-10. 10.1017/S0959270916000046.
Howell, S.N.G., Lewington, I. & Russell, W. (2014) Rare Birds of North America. Princeton Univ. Press.
Mullarney, K., Svensson, L., Zetterstrom, D. & Grant, P.J. (1999) Collins Bird Guide, Harper Collins