BirdForum is the net's largest birding community, dedicated to wild birds and birding, and is absolutely FREE! You are most welcome to register for an account, which allows you to take part in lively discussions in the forum, post your pictures in the gallery and more.
L. a. mongolicus in southeast Altai and Lake Baikal to Mongolia; winters southern Asia
European Herring Gull:
L. a. argentatus in Scandinavia and extreme northwest Russia, winters in northern and western Europe
L. a. argenteus in northwest Europe, winters to northern Spain
Gill and Donsker and Christidis et al. accept three species, with L. a. mongolicus as a subspecies of Vega Gull. Burger et al.  recognize two species, with American, Vega and Mongolian Gulls lumped under the name "Arctic Herring Gull."
Breeds mainly along rocky coastlines on cliffs, stacks and islands, in some areas on buildings or on flatter areas of shore and in others at inland lakes. Mainly coastal when not breeding but increasingly in urban areas and on farmland. Abundant at refuse-tips and around fishing harbours.
Collinson, J.M., Parkin, D.T., Knox, A.G., Sangster, G. & Svensson, L. (2008) Species boundaries in the Herring and Lesser Black-backed Gull complex. Brit. Birds 101(7): 340â€“363.
Burger, J., Gochfeld, M., Kirwan, G.M., Christie, D.A. & Garcia, E.F.J. (2018). European Herring Gull (Larus argentatus). 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/53982 on 27 August 2018).
Howell, S.N.G. and Dunn, J. (2007) A Reference Guide to the Gulls of the Americas. Peterson Field Guides, New York.
Malling Olsen, K. & Larsson, H. (2003) Gulls of Europe, Asia and North America. Christopher Helm, London.
Nisbet, I. C. T., D. V. Weseloh, C. E. Hebert, M. L. Mallory, A. F. Poole, J. C. Ellis, P. Pyle, and M. A. Patten (2017). Herring Gull (Larus argentatus), version 3.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.hergul.03