Rook (Corvus frugilegus) - HBW 14, p. 625

Taxonomy: Corvus frugilegus Linnaeus, 1758, Europe = Sweden.
Has been suggested that this species could form a superspecies with C. capensis, but there are major differences between the two, not least in nesting habits, the most apparent similarity between them being the pointed bill. Races possibly merit treatment as separate species; although breeding ranges not known to meet (200 km apart at nearest points), intermediates are said to occur in foothills of Altai and Sayan Mts; further research required. Proposed races tschuii (described from Gilgit, in N Pakistan) and ultimus (from Russian Altai) are on average smaller and finer-billed than other taxa, but differences considered trivial and both are synonymized with nominate; populations of E Siberia, Mongolia and NE China described as race centralis, tending to be slightly larger and with a more purplish sheen than pastinator, but differences considered clinal and insufficient to warrant naming of additional race. Two subspecies currently recognized.