Adams (2013) recognizes the smaller race E. n. nana confined to New Caledonia and the Loyalty Islands; while Clements/eBird & HBW recognizes the darker E. n. parryi from NW Australia. However geographic variation is slight and HANZAB, IOC & H&M4 all consider the species to be monotypic. Species is sometimes placed in the genus Ardea. Canon PowerShot SX60 HS.
References:
Adams, R. 2013 [updated 2015]. White-faced heron. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
Hancock, J. & J.Kushlan. 1984. The Herons Handbook. Harper & Row, New York.
Marchant, S. & Higgins, P.J. (editors) 1990. Handbook of Australian, New Zealand & Antarctic Birds. Volume 1, Ratites to Ducks. Melbourne, Oxford University Press.
Martínez-Vilalta, A., Motis, A., Kirwan, G.M. & Bonan, A. (2017). White-faced Heron (Egretta novaehollandiae). 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/52691 on 12 February 2017)