hide announcement WIN your very own meteorite! Subscribe, gift or renew a subscription to Cosmos and automatically go into the draw – Shop now!

Great tits show natural selection at work


Backyard bird-feeders are causing great tits to evolve longer beaks, writes Stephen Fleischfresser.


A great tit sitting on a branch.
A great tit sitting on a branch.
Dennis van de Water.

A little bird with an unfortunate name is providing scientists with ringside seats to evolution.

Parus major, commonly known as the great tit, is handing scientists a rare glimpse of the inner workings of natural selection, as the species’ beak lengthened over a 25-year period.

And the British obsession with bird feeding may be to blame.

In research published in Science, a team from the Netherlands Institute of Ecology and the universities of Wageningen, Oxford, Exeter, East Anglia, and Sheffield outline the evidence for this case of evolution in action.

Tracking evolutionary change is notoriously difficult: researchers need to identify the physical characteristic, called the phenotype, that is being selected, the genetic basis for the trait and the way it effects an organism’s fitness, as well as the factor in the environment driving the selection. Further complicating the picture is that there is rarely detailed information on the organism’s behaviour or ecology.

However, by bringing together ongoing projects of many different research institutions, the team of scientists lead by Mirte Bosse and Lewis Spurgin have managed to cover all the bases. Using historical genetic, behavioural, morphological and ecological data going back 70 years, combined with real-time tracking across three field sites, one in the UK and two in the Netherlands, the researchers have been able to assemble the necessary evidence.

What they found is intriguing.

By comparing the continental and British populations, Bosse and Spurgin discovered the bill of the British bird has become longer: a phenotype that clearly seems to be under selection. Although only clocking in at a fraction of a millimetre per year, the beak elongation is statistically significant.

The researchers were also able to pin down an underlying genetic basis for the longer beaks, some of which was closely associated with bill size in another famous bird population, Darwin’s finches. They were then able to determine a greater prevalence of these genes in the UK Parus major population, which were also “positively associated with fledgling production” and thus improved fitness.

The final piece of the puzzle is the environmental factor driving this selection. Noting that in similar documented cases change in bill-length “is typically associated with variation in food availability,” the authors attempted to identify the driver of selection by investigating food sources. While the wild diet of both continental and British great tits is the same, the one key difference was people.

“In the UK we spend around twice as much on birdseed and birdfeeders than mainland Europe – and we’ve been doing this for some time,” says Spurgin. The researchers’ analysis of UK great tit behaviour, done via radio tagging and automated birdfeeders, showed that birds with the genes for longer bills do in fact use birdfeeders far more. The research, then, likely indicates that Parus major is adapting its beak to be better able to stick it into garden birdfeeders.

Taken together, the “results provide a detailed example of natural selection in a wild animal” and an uncommon, and welcome, insight into the evolutionary process and our unwitting role in it.

Stephen fleischfresser.jpg?ixlib=rails 2.1
Stephen Fleischfresser is a lecturer at the University of Melbourne's Trinity College and holds a PhD in the History and Philosophy of Science.
Latest Stories
MoreMore Articles