Photo: Dark-eyed Junco, Judith Blakeley
Dark-eyed Juncos Vary Depending on Where They Live
Jessica Bigger
The Dark-eyed Junco is one of the most widespread species throughout North America, yet the variation in plumage and behavior between regional species is significant. According to a research paper by Ellen D. Ketterson, presented at the American Society of Naturalists, June 2015 in São Paulo, Brazil, Ketterson identified 8-11 subspecies. Seven of those subspecies display genetic variations. Six of these subspecies are different due to their environment. Some species have a larger range, like the Slate-colored Junco (right in our backyard), who ranges from Alaska all the way to the northeast; while others have a smaller, more localized range, like the White-winged Junco and Gray-headed Junco.
Although genetically, Juncos are quite similar, environmentally each subspecies expresses different plumage and behavior depending on where they live. For example, a recent study, cited in Ketterson’s research paper, “revealed that the plumage differences in two subspecies are literally skin deep, more a function of gene expression than differences in gene sequence.”
Dark-eyed Junco, Judith Blakeley
Dark-eyed Juncos are known as the “snowbird”, because most spend their breeding season up in the mountains and then come down to urban areas in the winter. However, back in the 1980’s birders started noticing flocks foraging on campus at UCLA and other urban areas year-round. Male juncos who are notorious for being aggressive to other male and female juncos- especially during breeding season-became quite docile and were less afraid of humans. The males in this particular subspecies started to sing in a higher octave and some females were building nests up in trees rather than traditionally on the ground.
Pamela Yeh, Associate Professor of Ecology and Evolutionary Biology at UCLA, who studies juncos on campus wrote an article in All About Birds. She believes the species has been evolving at a rapid pace. They seem to be able to adapt to different environments, which might explain the difference in plumage color and behavior across the species. Even though each subspecies shows differences in plumage, these minor changes happened within the last few thousand years, according to Dr. Borja Mila, from Madrid’s National Museum of Sciences in an interview by the Junco Project. So, in evolutionary terms, these changes happened fairly recently and in a very short amount of time.
Our Slate-colored Juncos have finally returned to our backyards this winter. Knowing that each subspecies behaves differently, take some extra time to see what our feathered friends do differently from other Dark-eyed Juncos across the country.
Sources:
https://www.allaboutbirds.org/guide/Dark-eyed_Junco/overview
https://juncoproject.org/view-download/chapter3/index.html
https://www.journals.uchicago.edu/doi/full/10.1086/709699
https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.14878