Natural Selection in Your Backyard

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Sarah Mattonen
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7.44

How does this align with my curriculum?

A study on bird feeders and beak sizes shows how an everyday human activity can affect the evolution of another species.

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 by 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!

Great tits at a bird feeder on the left and a black-capped chickadee on a bird feeder on the right
Great tits at a bird feeder on the left and a black-capped chickadee on a bird feeder on the right (Sources: Hellado via Pixabay and Blohowiak via Pixabay).

The study investigated how differences in the two populations’ genotypes (genetic makeup) 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 (links) 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 did the study find about the size of the bird’s beaks?

The scientists found that, on average, the beaks of birds living in the U.K. were about half a millimetre longer than the beaks of birds living 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 is only about 13 mm long, even a small difference can be quite noticeable!

Graph showing bill length of mainland Europe and United Kingdom birds (A) and bill length plotted over time (B) (1982-2007)
Graph showing bill length of mainland Europe and United Kingdom birds (A) and bill length plotted over time (B) (1982-2007) (Source: Science, 358(6361), Figure 4).
Graph - Text version

Graph A shows that the average length of bills on birds in mainland Europe is approximately 12.75 mm and the average length of bills on birds in the UK is 13.25 mm.
Graph B shows that bill length has been increasing over time.

But why would the U.K. birds have longer beaks? 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 that causes a change in a 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 is a prime example of natural selection in which specific genetic traits allow birds to better adapt to their environment and have better survival and reproductive success. The idea is, if birds have a longer beak they are better able to access the food in the bird feeders. And indeed, the birds with the gene variant for longer beaks went on to be more successful in raising their chicks to fledgling. 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.

Did you know?

Great tits are increasingly killing birds and eating their brains - and climate change may be to blame.

Great tit chicks in a nest
Great tit chicks in a nest (Source: TaniaVdB via Pixabay).

 

This isn’t the first study to look at the evolution of beak characteristics. In the 1830s, on his famous visit to the Galapagos Islands 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. This is thought to have been one of the key inspirations for his theory of evolution.

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!

Starting Points

Connecting and Relating

  • Do you have a bird feeder at home? If so, what birds visit the feeder?
  • Have you noticed any differences in the beaks of birds that are common in your part of Canada? If so, how do they differ? 

Connecting and Relating

  • Do you have a bird feeder at home? If so, what birds visit the feeder?
  • Have you noticed any differences in the beaks of birds that are common in your part of Canada? If so, how do they differ? 

Relating Science and Technology to Society and the Environment

  • Humans feed birds because we like to have them in our environment and we enjoy seeing them up close. Is it right that humans are also playing a role in causing genetic mutations that might make the birds become more dependent on humans for food?

Relating Science and Technology to Society and the Environment

  • Humans feed birds because we like to have them in our environment and we enjoy seeing them up close. Is it right that humans are also playing a role in causing genetic mutations that might make the birds become more dependent on humans for food?

Exploring Concepts

  • What is a genotype? What is a phenotype?
  • How can a gene variant affect phenotype?
  • What role can unique environmental conditions play in natural selection? 
  • What does it take to have one species become two species?
  • Do you think that the black-capped chickadee (Poecile atricapillus) and great tit (Parus major) could have once been a single species? Explain.

Exploring Concepts

  • What is a genotype? What is a phenotype?
  • How can a gene variant affect phenotype?
  • What role can unique environmental conditions play in natural selection? 
  • What does it take to have one species become two species?
  • Do you think that the black-capped chickadee (Poecile atricapillus) and great tit (Parus major) could have once been a single species? Explain.

Nature of Science/Nature of Technology

  • Explain the research method used by the scientists in the study discussed in the article.

Nature of Science/Nature of Technology

  • Explain the research method used by the scientists in the study discussed in the article.

Media Literacy

  • Superheroes in comics are sometimes the result of a genetic mutation. Can you think of a specific superhero and describe the phenotype of the genetic mutation they possess?

Media Literacy

  • Superheroes in comics are sometimes the result of a genetic mutation. Can you think of a specific superhero and describe the phenotype of the genetic mutation they possess?

Teaching Suggestions

  • This article can be used for Biology teaching and learning related to the topics of natural selection, evolution, heredity and populations. Concepts introduced include evolving, natural selection, populations, genotype, phenotype, gene variant and nucleotide. 
  • After reading this article, teachers could have students complete a Concept Definition Web learning strategy to consolidate their understanding of the term natural selection. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • To include some hands-on science, consider setting up a bird feeder where you can see it from your classroom and have students plan an inquiry to study some aspect of birds coming to the feeder (seed preferences, species that visit, preferred feeding times, etc.).

Teaching Suggestions

  • This article can be used for Biology teaching and learning related to the topics of natural selection, evolution, heredity and populations. Concepts introduced include evolving, natural selection, populations, genotype, phenotype, gene variant and nucleotide. 
  • After reading this article, teachers could have students complete a Concept Definition Web learning strategy to consolidate their understanding of the term natural selection. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • To include some hands-on science, consider setting up a bird feeder where you can see it from your classroom and have students plan an inquiry to study some aspect of birds coming to the feeder (seed preferences, species that visit, preferred feeding times, etc.).

Learn more

The Theory of Evolution (2011)

Article from The Conversation that explains natural selection and inheritance.

References

Bosse, M., Spurgin, L., Laine, V., Cole, E., Firth, J., & Gienapp, P. et al. (2017). Recent natural selection causes adaptive evolution of an avian polygenic trait. Science, 358(6361), 365-368. DOI: 10.1126/science.aal3298

Jones, D. N., & James Reynolds, S. (2008). Feeding birds in our towns and cities: a global research opportunity. Journal of Avian Biology, 39(3), 265-271. DOI: 10.1111/j.0908-8857.2008.04271.x

Orros, M. E., & Fellowes, M. D. (2015). Wild bird feeding in an urban area: intensity, economics and numbers of individuals supported. Acta Ornithologica, 50(1), 43-59. DOI: 10.3161/00016454AO2015.50.1.006