The true crows are large passerine birds that comprise the genus Corvus in the family Corvidae. Ranging in size from the relatively small pigeon-sized jackdaws (Eurasian and Daurian) to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopia, the 40 or so members of this genus occur on all temperate continents (except South America) and several offshore and oceanic islands (including Hawaii).

The crow genus makes up a third of the species in the corvid family. Other corvids include rooks and jays. Crows appear to have evolved in Asia from the corvid stock, which had evolved in Australasia. A group of crows is called a "murder," though this term usually appears in poetry rather than scientific contexts.

Systematics

The genus was originally described by Linnaeus in his 18th century work Systema Naturae. The name is derived from the Latin corvus meaning "raven". The type species is the Common Raven (Corvus corax); others named in the same work include the Carrion Crow (C. corone), the Hooded Crow (C. cornix), the Rook (C. frugilegus), and the Jackdaw (C. monedula).

There is no good systematic approach to the genus at present. Generally, it is assumed that the species from a geographical area are more closely related to each other than to other lineages, but this is not necessarily correct. For example, while the Carrion/Collared/House Crow complex is certainly closely related to each other, the situation is not at all clear regarding the Australian/Melanesian species. Furthermore, as many species are similar in appearance, determining actual range and characteristics can be very difficult, such as in Australia where the five (possibly six) species are almost identical in appearance.

The fossil record of crows is rather dense in Europe, but the relationships among most prehistoric species is not clear. Jackdaw-, crow- and raven-sized forms seem to have existed since long ago and crows were regularly hunted by humans up to the Iron Age, documenting the evolution of the modern taxa. American crows are not as well-documented.

A surprisingly high number of species have become extinct after human colonization, especially of island groups such as New Zealand, Hawaii and Greenland

Species

• Australian Raven C. coronoides
• Forest Raven C. tasmanicus
• Relict Raven C. (t.) boreus
• Little Crow C. bennetti
• Little Raven C. mellori
• Torresian Crow C. orru (also known as the Australian crow)
• New Caledonian Crow C. moneduloides
• Long-billed Crow C. validus
• White-billed Crow C. woodfordi
• Bougainville Crow C. meeki
• Brown-headed Crow C. fuscicapillus
• Grey Crow C. tristis
• New Ireland Crow, Corvus sp. (prehistoric)