Above: Great tits eat from a bird feeder
Image ©
Vassiliy Vishnevskiy,iStockPhoto.com

Have you ever had a bird feeder or put out bird seed in your yard to attract birds? Watching birds outside our homes can be a popular year-round activity for a lot of us. But behind this seemingly simple activity lies something significant. By attracting birds to your backyard, you might actually be impacting how these birds are evolving!

A 2017 study from a group of scientists from the Netherlands and the United Kingdom (U.K.) studied two populations of great tits, a small bird similar to a chickadee that you might see in your backyard. These are popular birds to study - they live in many places, there’s a lot of them, and they’re very eager to use backyard feeders!

Did you know? Great tits can adapt their breeding time to when there is the highest amount of food available. This way, they’re better fit to take care of their young.

The study investigated how differences in the the two populations’ genotypes (genetic makeups) translated into differences in their phenotypes (observable traits). For example, a bird’s beak size is part of its phenotype.

The study revealed fascinating correlations between beak sizes and bird feeders. Let’s look at this study in more detail. Then let’s look at how these little birds might be a great example of natural selection.

What the study found

The scientists found that, on average, U.K. birds’ beaks were about half a millimetre longer than bird beaks in the Netherlands.

In fact, since 1970, the beak sizes of the U.K. birds have increased by about a tenth of a millimeter. This may not seem like a lot, but when a great tit’s beak length is around 13 mm, even a small difference can be quite noticeable!

But why would the U.K. birds have a longer beak? Studies have shown that around half of U.K households feed birds in their gardens. The U.K. also spends about twice as much on birdseed and birdfeeders than other areas of Europe. According to this most recent study, the changes in the great tit could reflect the fact that over the past few decades, more and more people are getting bird feeders.

What does this mean for great tit evolution?

A gene variant is an alteration to the DNA nucleotide sequence causing a change in phenotype. The scientists monitored birds with electronic tracking devices and found that the birds with the gene variant for a longer beak tended to visit bird feeders more than those birds with a gene variant for a shorter beak. This means that over time, the genetic variants have resulted in birds who visit bird feeders having slightly longer beaks. This trait is carried on over generations of great tits.

Another interesting finding is that the birds with the gene variant for longer beaks were more successful in raising their chicks to fledging. This is a prime example of natural selection. Specific genetic traits allow these birds to better adapt to their environment. The idea is, if birds have a longer beak, they are better able to access the food in the bird feeders. Thanks to this, they have a better chance at surviving and reproducing, and more time to invest in taking care of their chicks.

Summing up...

Natural selection is happening all around us, sometimes in places we don’t expect it! So, the next time you put out bird seed in your backyard and watch the birds at your feeder, remember that small evolutionary changes are happening around you - even in your own backyards!

Did you know? This isn’t the first study to look at the evolution of beak sizes. In the 1830’s, Charles Darwin discovered that beak shape varied among species of finches. He found that each beak helped the birds acquire a specific type of food.

Let’s talk about it!

Do you know of any other examples of animals whose evolution might be getting impacted by humans interacting with them? Or can you think of some that might be interesting to study?

Learn more!

DNA and Evolution (2013)
CurioCity by Let’s Talk Science

Alleles and genes (2014)
Khan Academy

Can genetic engineering happen naturally? (2015)
CurioCity by Let’s Talk Science

Gene Expression (2014)


Recent natural selection causes adaptive evolution of an avian polygenic trait (2017)
Bosse M, Spurgin LG, Laine VN, Cole EF, Firth JA, Gienapp P, Gosler AG, McMahon K, Poissant J, Verhagen I, Groenen MA, Science

Who started first? Bird species visiting novel birdfeeders (2015)
Tryjanowski P, Morelli F, Skórka P, Goławski A, Indykiewicz P, Møller AP, Mitrus C, Wysocki D, Zduniak P, Scientific Reports

Wild bird feeding in an urban area: intensity, economics and numbers of individuals supported (2015)
Orros ME, Fellowes MD., Acta ornithologica

Feeding birds in our towns and cities: a global research opportunity (2008)
Jones DN, James Reynolds S., Journal of avian biology

An introduction to evolution (2018)
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Natural selection and Darwin’s finches (1991)
Grant PR, Scientific American

Adaptive phenotypic plasticity in response to climate change in a wild bird population (2008)
Charmantier A, McCleery RH, Cole LR, Perrins C, Kruuk LE, Sheldon BC, Science

Sarah Mattonen

I’m originally from Thunder Bay, Ontario and am currently a NSERC postdoctoral scholar at Stanford University in California. I completed my PhD in Medical Biophysics at the University of Western Ontario in London, Ontario. My research focuses on medical image analysis to improve outcomes for cancer patients. I love sharing my passion for science and research with others. In my spare time I like to enjoy nature, live music, and sports.

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