Do ‘Birds Of A Feather’ Speciate Together?

Although they look dramatically different, carrion crows and hooded crows are almost indistinguishable genetically, and hybrid offspring are fertile, but the two forms remain distinct mostly due to the dominant role of plumage color in mate choice

by GrrlScientist for Forbes | Twitter | Newsletter

NOTE: This piece was a Forbes Editor’s pick.

Carrion crow (Corvus corone) and (right) hooded crow (Corvus cornix) are the same species, genetically speaking, except for genes involved with plumage color. The two forms rarely hybridize and thus, are apparently undergoing the process of diverging into two genetically distinct species. (Images: Leander Khil, courtesy of Matthias Weissensteiner. Collage created by Bob O’Hara.)

If you’ve ever visted or lived in Germany, as I have, you simply must visit the River Elbe. This river is the location of the most remarkable division between two bird species that I’ve ever seen. On the western shore lives the the jet-black carrion crow, Corvus corone, whilst the grey-bodied hooded crow, C. cornix, predominates on the eastern shore.

Scientists have been fascinated by this remarkable natural boundary too, because the two crow species are genetically indistinguishable, yet even a casual human observer would agree that they look dramatically different. The crows agree too: the two forms almost never interbreed, but yet, when they do, they produce fertile hybrid offspring. These fascinating peculiarities have made these two crows a popular model amongst scientists who study evolution and how new species arise.

“Defining speciation as the buildup of reproductive isolation, carrion crows and hooded crows are in the…