Birdfeeders causing great tits to evolve longer beaks

London

A British enthusiasm for feeding birds and the widespread use of birdfeeders may have caused UK's great tits to have longer beaks than their counterparts in other countries, a study has found.

The findings, published in the journal Science, identified for the first time the genetic differences between UK and Dutch great tits, which researchers were then able to link to longer beaks in UK birds.

Using genetic and historical data, researchers also found that the differences in beak length had occurred within a relatively short time frame.

This led them to speculate that there may be a link with the relatively recent practice of putting out food for garden birds.

Researchers, including those from University of Wageningen and University of Oxford in the UK, screened DNA from more than 3,000 birds to search for genetic differences between the British and the Dutch populations.

These differences indicate where natural selection might be at work.

The specific gene sequences that had evolved in the British birds were found to closely match human genes known to determine face shape.

There were also strong similarities with genes identified with beak shape in Darwin's study of finches  — one of the best-known examples of how physical traits have adapted to different environments in the wild.

This led the researchers to think that great tit beaks were evolving by natural selection in British great tits, perhaps in response to the widespread use of bird feeders.

Researchers at Oxford University have been studying the Wytham Woods great tit population in Oxfordshire for 70 years and so the team had access to a wealth of historical data, which clearly showed that the British great tits' beaks were getting longer over time.

They were also able to access data from electronic tags fitted to some of the Wytham Woods birds, which enabled them to track how much time was spent at automated bird feeders.

"Between the 1970s and the present day, beak length has got longer among the British birds. That's a really short time period in which to see this sort of difference emerging," said Jon Slate, from the University of Sheffield in the UK.

"We now know that this increase in beak length, and the difference in beak length between birds in Britain and mainland Europe, is down to genes that have evolved by natural selection," Slate said.

The team also found that birds with genetic variants for longer beaks were more frequent visitors to the feeders than those birds which did not have that genetic variation. PTI