Rare ancestors of pigeons take refuge on small Scottish islands

July 1 () –

Researchers led by members of the Oxford University Biology Department have found rare colonies of wild ancestors of common and feral domestic pigeons.

Already extinct in England and Wales, the wild rock pigeon (Columba livia) has been found on isolated islands of Scotland and Irelandwhich provides information on how the domestic pigeon came to be.

“Wild” pigeons originate from escaped domestic birds and can be seen in towns and cities around the world. These domestic pigeons are descended from wild rock pigeons, They nest in sea caves and mountainous areas.

Despite the success of feral pigeons, the rock pigeon has been declining throughout its global range, which once encompassed vast areas of Africa, Asia, and Europe. University of Oxford Ph.D. student and lead author Will Smith says “studying the decline of the rock pigeon has been challenging for researchers due to extensive interbreeding and replacement with feral pigeons.”

Rock pigeons now persist only in small, relict populations where feral pigeons have not yet been able to colonize. In fact, due to the interbreeding of feral and rock pigeons, and their resulting hybrids, many ornithologists believe that there are no truly wild rock pigeons left. However, there are potential colonies in certain places, including, in Europe, the Faroe Islands, parts of the Mediterranean, and parts of Scotland and Ireland.

The researchers studied populations of birds believed to be rock pigeons in Scotland and Ireland using DNA analysis to determine whether the birds were truly wild and to estimate how much genetic influence of feral pigeons different wild populations had experienced.

Through a combination of expeditions and collaboration with British Trust for Ornithology bird banders, the research team captured putative feral pigeons and rock pigeons in places including North Uist in the Outer Hebrides, Orkney and Cape Clear Island.

The team took feather samples from the birds for DNA analysis. By sequencing the DNA of the pigeons, they were able to show the differences between feral and rock pigeons, and also measure the degree of interbreeding between the two forms of the species.

The results confirmed that UK and Irish rock pigeons descend from the undomesticated lineage from which all feral and domestic pigeons originate, with varying degrees of interbreeding. Orkney rock pigeons have undergone extensive interbreeding with feral pigeons and are at risk of hybridizing to the point of extinction as a distinct lineage. By contrast, rock pigeons in the Outer Hebrides, belonging to Scotland, they remain almost free from the influence of feral pigeons.

“We identified feral pigeon ancestry in most of the Scottish and Irish rock pigeon populations we sampled, and there have been feral pigeons in Europe for hundreds of years. It was therefore really surprising to discover that the Outer Hebridean rock pigeons showed negligible signs of hybridisation.Will Smith explained.

However, feral pigeons have been reported on these islands with increasing frequency, so it could be that the distribution of feral rock pigeons in the UK continues to decline as a result.

Recording their distribution and genetic status will help monitor remaining rock pigeon populations. and will encourage efforts to understand possible relict populations elsewhere.

In the broader context of conservation, a greater understanding of “extinction by hybridization” will help efforts to prevent many other plants and animals, such as the Scottish wildcat, from suffering the same fate as the rock pigeon.

The article is published in iScience.