Barn owls are one of the most widely distributed birds, being found on six continents. In Europe, they follow a general pattern: southern areas host pale owls and聽darker birds dominate in the north. But barn owls in the UK and Ireland are consistently a stark white, and a new analysis explains why.
studied the聽owls (Tyto alba) while at the聽University of Lausanne in聽Switzerland. She and her colleagues analysed DNA from 147聽barn owls across six European populations.聽They targeted a gene called MC1R, which is known to influence feather pigmentation in barn owls, along with 22 other genes the owls carry that have been linked to feather colour.
In particular, they were looking for聽evidence that owls from Ireland and the UK had dark-feathered ancestors and then聽underwent strong selection for pale feathers, as an adaptation to local conditions. They didn鈥檛 find any.
Advertisement
鈥淲e didn鈥檛 see that one coming,鈥澛爏ays Machado, so they began looking for an alternative explanation. She and her colleagues used聽data on the habitats that barn owls occupy today to predict how they would have been distributed across Europe under ancient climatic conditions.
This revealed a聽now-submerged land corridor of suitable owl habitat along the Bay of Biscay, bridging Iberia and the Ireland-UK region some 20,000 years ago.
This suggests owls in the UK and Ireland had pale-feathered ancestors from southern Europe.聽The genetic data corroborates this, showing that owls from the region have close relations with those from Portugal.
The Iberian route is a surprise. Most animals that recolonised the UK and Ireland after the Pleistocene ice sheets retreated around 18,000 years ago are thought to have entered via Doggerland, a boggy land bridge that existed at the time and connected Belgium with southern England.
But Machado suspects that, as more genetic data is studied, evidence will emerge that other animals reached the region along the Iberian route.
at the Swedish Museum of Natural History in Stockholm says that the study is 鈥渃ompelling鈥�. He says it would be interesting to investigate whether the barn owls of the UK and Ireland originated as a small population, and if so whether this affected their adaptability.
Machado says future work should seek to more fully understand how genetics determine the owls鈥� colour. There are also behavioural differences to study: the barn owls of the UK and Ireland regularly hunt in the day, unlike those in mainland Europe.
Molecular Ecology
Sign up to Wild Wild Life, a free monthly newsletter celebrating the diversity and science of animals, plants and Earth鈥檚 other weird and wonderful inhabitants
