Very similar to Willow Tit (Poecile montanus), Marsh Tit is much more common in Hokkaido, especially in the lowlands. Marsh Tit has an interesting distribution with disjunct populations in Europe and East Asia separated by over 1,000 km. Asian Marsh Tits average slightly larger bills and smaller feet but genetic differences are minimal. Geographic variation is complex. The population on Hokkaido is usually assigned to the race P. p. hensoni characterized by slightly paler coloration and shorter tail as seen here. Formerly included in the genus Parus. Canon PowerShot SX50 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. (2017). Marsh Tit (Poecile palustris). 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 http://www.hbw.com/node/59859 on 24 June 2017).
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