Evolution works very slowly — except when it doesn’t. New research shows that certain British birds appear to be changing quickly as result of bird feeders, evolving longer beaks to help them access the food inside.
Image: University of Oxford
Many years ago, the late evolutionary biologist Stephen Jay Gould proposed a concept he called “punctuated equilibrium,” in which species undergo rapid bursts of evolution in reaction to a sudden environmental change. And to that point: Research published today in Science suggests that populations of great tits (Parus major) are in the midst of a punctuated equilibrium phase thanks to the relatively recent introduction of backyard feeders.
Specifically, the birds are evolving longer beaks, which helps them access food, and in turn boosts their chances of reproducing and passing this fortuitous trait down to the next generation. It’s classic Darwinian natural selection in action — but at an accelerated pace.
The new research, led by the University of Oxford’s Department of Zoology, is part of a long term study of populations of great tits (Parus major) in the UK’s Wytham Woods and in Oosterhout and Veluwe, in the Netherlands. Oxford University has been studying the Wytham Woods great tit population for over 70 years.
A pair of great tits. (Image: Wikimedia commons)
For the study, the researchers scanned the DNA of more than 3000 birds in an effort to find genetic differences between the British and Dutch populations. The analysis revealed altered gene sequences linked to facial features, leading the researchers to speculate that the beaks of great tits were adapting to the widespread use of bird feeders.
To see if this might be the case, the researchers took a gander at the rich historical record, and it showed that the British version of the great tit has a beak that appears to be getting longer over time. Further, they had access to data from electronic tags that were fitted to some of the Wytham Woods birds, allowing the researchers to track how often these birds were frequenting bird feeders.
As expected, birds with genetic markers for longer beaks visited bird feeders more regularly than birds without the genetic variation.
“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, a co-author of the new study and a professor at the University of Sheffield, in a statement. “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.”
In the United Kingdom, Britons spend about twice as much on birdseed and bird feeders than the folks in mainland Europe — and they have been engaging in this backyard activity for quite some time.
“In fact, at the start of the 20th century, Punch magazine described bird feeding as a British national pastime,’ said study co-author Lewis Spurgin, of the School of Biological Sciences at the University of East Anglia (UEA). “Although we can’t say definitively that bird feeders are responsible, it seems reasonable to suggest that the longer beaks amongst British great tits may have evolved as a response to this supplementary feeding.”
The researchers also discovered that birds with the long-beak genetic variants were better at reproducing than their short-beaked counterparts. From a “survival of the fittest” standpoint, this suggests that the newly acquired trait is a fortuitous one — one that’s leading these birds down a new evolutionary path. Given enough time and assuming Britons don’t alter their bird feeding habits, this could eventually result in the emergence of an entirely new subspecies of great tit, an evolutionary process that biologists refer to as speciation.
The avenues for future research are obvious, and the researchers have already begun to look at the DNA of other great tit populations in Europe. Early results show that the emerging long-beak genetic variant is exclusive to the UK. Other researchers in other parts of the world should take note and embark on similar studies to see if similar things are happening to birds elsewhere.
As a final note, bird feeders may make it easier for birds to find food, but it also makes it easier for cats to find birds. If you’re a cat owner, you should probably keep them away from backyard feeders.
[Science]