Sometimes considered conspecific with E. leucocephalos, but clear differences in plumage, as well as in behaviour and osteology, support treatment as separate species. The two hybridize extensively in W & C Siberia (across c. 3000 km in taiga and forest-steppe zone from R Ural E to L Baikal), and intensity of interbreeding is increasing, since each species is expanding its breeding range across/towards that of the other; this type of interbreeding has been described as intermediate between occasional hybridization (not influencing gene pools of parent species) and introgressive hybridization (resulting sometimes in local fusion of species). An independent analysis of phylogeny supports recognition of two independent species, although cytochrome b sequences very similar, giving strong indication that they are sister-species; sharing of haplotypes even in very distant locations seems to be result of introgression of mtDNA. Independent alternative study also argues that both species are older than their closest relatives and that mtDNA has recently introgressed between them, likely as result of selective sweep. Has been suggested that race erythrogenys is product of hybridization with E. leucocephalos. Nominate race intergrades with erythrogenys in broad zone from Baltic republics, W European Russia and W Belarus S to E Hungary, E & S Balkans and Greece. Three subspecies recognized.
Introduced in New Zealand region.
Food and feeding
Status and conservation
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