Research maps ‘wild’ rock pigeon populations in Britain and Ireland

A new article published today [1 July] revealed that Britain and Ireland still have wild rock pigeons surviving on some islands, but ‘pure’ populations are limited and many face a growing threat from growing numbers of wild birds.

Feral pigeons, widely known as feral pigeons, originate from escaped domestic birds and can be seen in cities around the world. These wild and domestic pigeons are descended from feral rock pigeons, which nest in sea caves and mountainous areas. Unlike the success of Feral Pigeon, Rock Dove has declined throughout its global range – which once encompassed large swaths of Afro-Eurasia. Its decline has been difficult to study as it occurred due to extensive cross-breeding and eventual replacement with feral pigeons.


A feral pigeon on Lewis, Outer Hebrides (Ed Stubbs).

Rock pigeons now only persist in relict populations where feral pigeons have not yet colonized. In fact, given the difficulties in distinguishing between feral pigeons, rock doves and their hybrids, many birders claim that truly wild rock doves no longer exist despite the existence of potential colonies in some places, including , in Europe, the Faroe Islands, parts of the Mediterranean and parts of Scotland and Ireland.

Will Smith and his colleagues have studied possible rock dove populations from parts of Scotland and Ireland by analyzing their DNA. They wanted to determine whether these birds were really “wild”, and also what genetic influence of wild pigeons the different populations suffered.

Through a combination of expeditions and working with BTO banders, they have caught both wild pigeons and putative rock doves in places like North Uist in the Outer Hebrides, Orkney and Cape Clear Island. Unlike their wild relatives, rock doves are very shy and wary of people, so catching the birds proved difficult.

The team took feather samples from the birds and brought them back to Oxford for DNA analysis. By sequencing the DNA of pigeons, they were able to highlight the differences between wild pigeons and rock doves, and also measure the degree of interbreeding between the two forms.

They found that the putative doves from the UK and Ireland are likely descended from the undomesticated lineage of the species. While the rock doves of the Orkneys, for example, have undergone extensive interbreeding with feral pigeons and are therefore likely doomed to extinction as a separate evolutionary line, the rock doves of the Outer Hebrides remain almost entirely free from the influence wild pigeons.



The maximum likelihood topology of a VCF of 871,968 SNPs and 121 birds, using IQTREE-2, shows a split between feral rock pigeons and feral/domestic pigeons and captive rock pigeons. This division is supported by superfast bootstrap support values ​​of 100%. Hill Pigeon Columba rupestris was used as an outgroup. Within the Rock Dove clade, there is a well-supported geographic structure.

Given that both wild and domestic pigeons have been present in Europe for thousands of years, it was a great surprise that rock pigeons from the Outer Hebrides managed to persist, in a form lacking any significant genetic contribution from their parents. common, for so long.

Worryingly, feral pigeons are being seen on these islands with increasing frequency, so it could be that the distribution of feral rock pigeons in the UK is continuing to shrink.

Having a better idea of ​​their distribution and genetic status will help efforts to monitor remnant rock pigeon populations and encourage more efforts to understand potential relict populations within their global range.

Increasing our understanding of “extinction by hybridization” will help conservation efforts to prevent many other animals and plants from suffering the same fate as the Rock Dove.

Reference

Black-smith et al. 2022. Limited domestic introgression in a last refuge of the feral pigeon. iScience. DOI: https://doi.org/10.1016/j.isci.2022.104620

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