Carrion Crow (Corvus corone) - HBW 14, p. 629

Taxonomy: Corvus Corone Linnaeus, 1758, England.
Thought to form a superspecies with C. cornix, possibly also including C. pectoralis; was for long treated as conspecific with former. Situation complex, as narrow bands of hybridization between present species and C. cornix exist across Scotland, through C Europe, in C Siberia and in C Asia, but striking plumage differences, subtle differences in vocalizations, and both narrowness and plasticity of hybrid zones all suggest that speciation has been at least partially achieved. Presence of "black crows" over both W & E regions of Eurasian landmass, separated by C. cornix, is noteworthy; preliminary research indicates that these black populations may merit treatment as two separate species, but more extensive investigation required. Within extensive range of E populations (orientalis) there is a cline of increasing bill size from W to E, which has prompted the describing of a further three races: interpositus (described from Japan), saghalensis (from Sakhalin I) and yunnanensis (from S Yunnan, in China) are all regarded as synonyms of orientalis. Two subspecies currently recognized.