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Caucasian Lark E. a. penicillata, adult - note extensive black mask Photo by baharro AladaÄźlar National Park, Turkey; May 2006
Circumpolar; tundra, and south in mountain plateaux, plains and semi-deserts to the Atlas Mountains in northwest Africa, the Balkans in Europe, the Zagros and Himalaya in Asia, and the northernmost Andes in the Americas. Arctic populations are strongly migratory, while southern mountain populations are resident or short-distance altitudinal migrants.
Complex. The currently accepted broad circumscription of a single species with 42 subspecies has recently been shown to leave the species paraphyletic with respect to the closely related Temminck's Lark; a split into six species (as arranged below) is likely to be accepted formally in the near future.
Of interest as the sole species of a diverse Old World family to have colonised the New World; a similar example in reverse is the Eurasian Wren.
Drovetski, S. V., RakoviÄ‡, M., Semenov, G., Fadeev, I. V., & Red'kin, Y. A. (2014). Limited phylogeographic signal in sex-linked and autosomal loci despite geographically, ecologically, and phenotypically concordant structure of mtDNA variation in the Holarctic avian genus Eremophila. PLoS ONE 9 (1): e87570.
Birdforum thread discussing taxonomy of Horned Larks (post #20 et seq. for recent research)