Rare wild ancestors of pigeons could help prevent 'extinction by hybridization'

The species that occupied Darwin's studies could help further scientists' understanding of genetics in the modern day.

 A rock dove (Columba livia) with a juvenile in a cliffside crevice at Berry Head, Brixham. (photo credit: Partonez/Wikimedia Commons)
A rock dove (Columba livia) with a juvenile in a cliffside crevice at Berry Head, Brixham.
(photo credit: Partonez/Wikimedia Commons)

Rare colonies of the wild ancestors of domestic and feral pigeons could help conservationists prevent species from being virtually wiped out as they become so mixed with other species that they're no longer a distinct species, according to new research by scientists led by members of Oxford University's Department of Biology.

"Feral" pigeons, the birds that can be seen eating breadcrumbs in many cities around the world, are descended from escaped domestic birds who are in turn descended from wild Rock Doves. While pigeons have been wildly successful in being fruitful and multiplying, their ancestors have not been as lucky.

Rock Doves were once present across vast areas of Africa, Asia and Europe. "Studying the decline of the Rock Dove has been challenging for researchers because of such extensive interbreeding and replacement with feral pigeons," said University of Oxford DPhil student and lead author Will Smith in an article on the university's website.

The doves are now only present in small populations where feral pigeons have not yet been able to colonize. Due to the extensive interbreeding between feral pigeons and Rock Doves, many ornithologists believe that there are no truly wild Rock Doves left.

The study

The researchers studied potential Rock Dove colonies in Scotland and Ireland by analyzing their DNA to determine if the birds were really "wild" and to see how much genetic influence feral pigeons had on wild populations.

 Two pigeons rest on a tree stump in St James’s Park, London, Britain, March 23, 2022 (credit: JOHN SIBLEY/REUTERS) Two pigeons rest on a tree stump in St James’s Park, London, Britain, March 23, 2022 (credit: JOHN SIBLEY/REUTERS)

The team took samples from both feral pigeons and possible Rock Doves for DNA analysis and were able to show the differences between feral pigeons and Rock Doves, as well as to measure the degree of interbreeding between the two.

In some locations, such as Orkney, the doves have experienced interbreeding to an extent that they are at risk of getting hybridized to the point that they will become extinct as a distinct lineage. In other locations, such as the Outer Hebrides, the doves are nearly free of any feral pigeon influence.

"We identified feral pigeon ancestry in most of the Scottish and Irish Rock Dove populations we sampled, and there have been feral pigeons in Europe for hundreds of years," said Smith. "It was therefore really surprising to discover that the Outer Hebridean Rock Doves showed negligible signs of hybridization."

The doves on the Outer Hebrides may not be out of the woods yet, as increasing numbers of feral pigeons have been reported on these islands, meaning that the number of wild Rock Doves may decrease there as well.

Recording the distribution and genetic status of the birds will help monitor the remaining populations and encourage efforts to understand potential populations elsewhere. Further study will also increase understanding of "extinction by hybridization," which could help other species, such as the Scottish wildcat, facing similar issues.

Darwin and pigeons

Before he wrote his work "On the Origin of Species," Charles Darwin raised pigeons in the garden of his country estate, seeing the diversity of pigeon breeds produced by breeders as a model of how natural selection works to produce the diversity of life in nature.

The scientists stressed that being able to study the Rock Dove offers an "unprecedented opportunity to study an undomesticated form in a natural setting," which could help enhance our understanding of the domestic pigeon as a model organism in biology to explore how domestication and hybridization work, according to the research published in iScience.