Engelmoer & Roselaar (1998) recognize four subspecies of Eurasian Whimbrel Numenius phaeopus i.e. nominate phaeopus from Scandinavia to ca. SW Taimyr; islandicus from Iceland to Scotland; alboaxillaris from the steppes between the lower Wolga to SE of the Urals; variegatus from Taimyr to NE Siberia. There are differences in size between the various subspecies but on the axillaries of islandicus the white parts are mostly not wider than the brown bars; in phaeopus the white parts are mostly wider than the brown bars; in alboaxillaris the axillaries are white or have a few brown bars at most; variegatus has a whitish lower back spotted with brown and a barred white rump while it's axillaries have broad brown bars.
Engelmoer, Meinte and Cees S.Roselaar. 1998. Geographical Variation in Waders. Kluwer Academic
Publishers.Dordrecht/Boston/London: ISBN 0-7923-5020-0