Microevolution in Tawny Owl

Study: Climate Change Drives Microevolution in a Wild Bird

    In this world, you have to adapt to climate change in order to survive. With the rising global temperatures, the winter season has shortened and become less intense. The tawny owl, Strix aluco, is commonly found in the woodlands of Europe and on east into parts of Russia. Over the past 50 or so years, it has been observed that the owl’s dominant coloring has changed into a dark brown rather than the original pale grey. “Here, we show that pheomelanin-based plumage coloration in tawny owls is a highly heritable trait” (Karell). This event is proving that natural selection in occurring and owls of the darker brown color are the ones surviving and reproducing.

Coloration seems to be dependent on snow and snow depth. When snow depth is higher 25+cm, there is a significant difference in survival rates between the two colorations of tawny owls (grey and brown). The grey had a largely higher survival rate, likely due to their ability to blend into their surroundings. However, as climate change warms the Earth, snow depth and intensity has declined. This decline in snow has allowed the brown tawny owls to better blend into their environment compared to the pale grey owls. The study took immigration and emigration into account by categorizing all the breeding individuals into different categories. Immigrants would represent unmarked new owls. Local recruits would represent “first breeders marked as young.” Lastly, old breeders represent survivors from previous breeding attempts, thus meaning they have been there a while. There was no observed productivity change in the brown coloration compared to the grey coloration, therefore it was concluded that the increase of brown tawny owls is due to warmer winters with lack of snow. This change in coloration that is driven by natural selection, or species change through time, is an example of microevolution. Microevolution is a prediction by Darwin’s idea of descent with modification. Each red dot represents the mean frequency of seven 5-year periods studied. The Y axis, dependent variable, represents the frequency of the brown coloring found, and the x axis, independent variable, represents the Year (time frame).

Reference:

Karell, P., Ahola, K., Karstinen, T. et al. Climate change drives microevolution in a wild bird. Nat Commun 2, 208 (2011). https://doi.org/10.1038/ncomms1213