Willow Tit in front and Japanese Tit in back. This species closely resembles the Marsh Tit (P. palustris) and characters which separate the two seem to change geographically. Here in the Honshu highlands, Willow Tit is the expected species and Marsh Tit does not occur. These birds are P. m. restrictus which is restricted to Japan. It is a small pale subspecies characterized by mostly white underparts, usually lacking buff-colored flanks. Geographic variation complex. Eleven to fifteen subspecies usually recognized depending on whether the Sichuan Tit (P.weigoldicus) of southwest China and the Songar Tit (P. songarus) of Central Asia are considered separate species. Formerly included in the genus Parus. Canon PowerShot SX60 HS.
References:
Brazil, M. (2009). Birds of East Asia. Princeton Univ. Press.
Eck, S., & Martens, J. (2006). Systematic notes on Asian birds. 49. A preliminary review of the Aegithalidae, Remizidae and Paridae. Zoologische Mededelingen, 80:1-63.
Gosler, A., Clement, P. & Garcia, E.F.J. (2019). Willow Tit (Poecile montanus). 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/59860 on 16 April 2019).
Harrap, S. & Quinn. D. (1995) Chickadees, Tits, Nuthatches & Treecreepers. Princeton Univ. Press.
Scott G.W. (1999) Separation of marsh tits parus palustris and willow tits parus montanus , Ringing & Migration, 19:4, 323-326, DOI: 10.1080/03078698.1999.9674201