Until recently C. unicolor, and more recently C. violaceus, treated as races of present species. Grouping of taxa exceedingly problematic, as little agreement evident in results of various studies, and published data frequently contradictory, while vocal analyses#R produce yet further complications; nevertheless, most races seem fairly distinctive in terms of morphology and/or plumage, and groups suggested here, while still very tentative, are based to large extent on such characters. Subspecies compilator recently split on account of its size and deep voice#R, and this almost certainly appropriate, yet genetically it appears close to race celebensis#R; more research needed. Birds on Mentawai Is (off Sumatra) traditionally included in nominate race, but this seems unlikely; research required. Form celebensis (with mangoli) recently elevated to species rank by some authors#R on basis of genetics and voice; birds from Banggai Is (off E Sulawesi) included in celebensis but may belong with mangoli and, likewise, birds reported on Karakelong (in Talaud Is) and Siau placed with celebensis but confirmation of race needed. Small Philippine races almost certainly represent one or more separate species; each exhibits substantial vocal differences from the other two#R. Research on all taxa called for. Recent sight record of a family party of crows resembling present species on W coast of Sumba, in Lesser Sundas, may represent an undescribed taxon. Seven subspecies recognized.
Food and feeding
Status and conservation
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