Despite their differing colourings, carrion crows and hooded crows are almost identical genetically.
20 June 2014
Hooded crows live mainly in eastern Europe, but interbreed with carrion crows from the west.
To the west, the skies belong to the carrion crow. To the east, the hooded crow rules the roost. In between, in a narrow strip running roughly north to south through central Europe, the twain have met, and mated, for perhaps as long as 10,000 years. But although the crows still look very different — carrion crows are solid black, whereas hooded crows are grey — researchers have found that they are almost identical genetically.
The taxonomic status of carrion crows (Corvus corone) and hooded crows (Corvus cornix) has been debated ever since Carl Linnaeus, the founding father of taxonomy, declared them to be separate species in 1758. A century later, Darwin called any such classification impossible until the term 'species' had been defined in a generally accepted way. But the definition is still contentious, and many believe it always will be.
The crows are known to cross-breed and produce viable offspring, so lack the reproductive barriers that some biologists consider essential to the distinction of a species, leading to proposals that they are two subspecies of carrion crow. In fact, evolutionary biologist Jochen Wolf from Uppsala University in Sweden and his collaborators have now found that the populations living in the cross-breeding zone are so similar genetically that the carrion crows there are more closely related to hooded crows than to the carrion crows farther west1.