DNA testing reveals that the wild ancestors of common domestic and feral pigeons, which are now extinct in many parts of the world, are still alive on Scottish and Irish islands.
Researchers from Oxford University’s Department of Biology discovered rare colonies of common domestic and feral pigeons’ wild ancestors.
The wild Rock Dove (Columba livia) has been discovered on secluded Scottish and Irish islands, providing insights into how the domestic pigeon came to be.
‘Feral’ pigeons are escaped domestic birds that can be found in towns and cities around the world. Domestic pigeons are descended from wild Rock Doves, which nest in sea caves and mountains.
Despite the success of feral pigeons, the Rock Dove’s global range has been shrinking 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 Will Smith, a DPhil student at the University of Oxford.
Rock Doves are now only found in small, relict populations where feral pigeons have yet to colonize. In fact, many ornithologists believe that there are no truly wild Rock Doves left due to interbreeding between feral pigeons and Rock Doves and the resulting hybrids. However, there are potential colonies in certain locations, such as the Faroe Islands, parts of the Mediterranean, and parts of Scotland and Ireland in Europe.
The researchers studied populations of Rock Doves in Scotland and Ireland using DNA analysis to determine whether the birds were truly ‘wild’ and to estimate how much genetic influence feral pigeons had on different wild populations.
The research team caught both feral pigeons and putative Rock Doves in places like North Uist (Uibhist a Tuath) in the Outer Hebrides, Orkney, and Cape Clear Island through a combination of expeditions and collaboration with British Trust for Ornithology bird ringers.
The team collected feather samples from the birds in order to conduct DNA analysis. They were able to show the differences between feral pigeons and Rock Doves by sequencing the pigeons’ DNA, as well as measure the degree of interbreeding between the two forms of the species.
The findings confirmed that Rock Doves in the United Kingdom and Ireland descended from the same undomesticated lineage as feral and domestic pigeons, with varying degrees of interbreeding. Rock Doves in Orkney have interbred extensively with feral pigeons and are in danger of becoming hybridized to the point of extinction as a distinct lineage. In contrast, feral pigeons have had little impact on Rock Doves in the Outer Hebrides.
“Feral pigeon ancestry was found in the majority of the Scottish and Irish Rock Dove populations studied, and feral pigeons have existed in Europe for hundreds of years. It was thus quite surprising to learn that the Outer Hebridean Rock Doves showed no signs of hybridization “Will Smith elaborated.
However, feral pigeons have been reported on these islands on an increasing basis, so the distribution of wild Rock Doves in the UK may be shrinking as a result.
Recording their distribution and genetic status will aid in monitoring the remaining Rock Dove populations and encourage research into potential relict populations elsewhere.
In the broader context of conservation, gaining a better understanding of ‘extinction by hybridization’ will aid efforts to save many other plants and animals, such as the Scottish wildcat, from the same fate as the Rock Dove.
The full paper, Limited domestic introgression in a wild pigeon’s last refuge, is available in iScience.
Reference: DOI: 10.1016/j.isci.2022.104620