You have no doubt seen these cute little birds hopping on the ground underneath your bird feeder in the winter, but you aren't the only one watching them! Scientists have studied this species extensively. Over 1,300,000 Juncos have been banded since 1955, and over 15,000 of the banded birds have been recovered.
Researchers at Indiana University have conducted numerous studies on Juncos. They built the Kent Farm Bird Observatory facility including indoor and outdoor free-flight aviaries for housing flocks of juncos. A recent I.U. study monitored the effects of testosterone on Juncos. Increased testosterone allowed males to win mates, but they lost interest in raising their young had a shorter lifespan (Ketterson, et al., Indiana University 2007). In 1994, I.U. scientists studied the ability of Juncos to survive in winter when food is scarce by tracking the variations in their fat reserves. They noted that Juncos choose different wintering latitudes as they age (Rogers, et al., Indiana University 1994).
Scientists in other areas of the country have also be studying Juncos extensively. Their movements over (or more typically around) hills were tracked for three years in New Jersey. Not surprisingly, the birds chose the lower altitudes whenever possible (Schaeffer, "North American Bird Bander" 1979). The Junco's increased oxygen demands in winter are met by the bird's ability to increase its oxygen-carrying capacity (Swanson, Oregon State University 1990). Scientists have even studied the preening oils of Juncos and found that Juncos can distinguish between males and females by the odor of the oils, and they can use the odor to determine whether a bird is larger or smaller. Surprisingly, the females seemed to prefer the smaller males in this study (Whittaker, et al., "Behavioral Ecology" 2011).
Why are Juncos studied so often? They are easy to observe! They are common and sociable so it is not difficult to find a large group. They come easily to feeders so it is a simple task to attract them to net sites.
The interest in this bird and volume of study has even resulted in a popular documentary: "The Ordinary Extraordinary Junco" (http://juncoproject.org/). The film was designed by Indiana University to be a revolutionary type of multimedia textbook, teaching high school and college students in 8 "chapters" about the scientific method, ecology, genetics, physiology and animal behavior. I.U. allows free screenings of the 88-minute film for non-profit organizations and independent theaters upon request, so if you want to learn more about Juncos, you might want to arrange a screening for your local Audubon Society. As Bob Duquesne stated in his review of the film in "BDN Maine Outdoors" , "I will never look at a junco the same way again... [T]his little gray bird has a lot to teach us, about birds and about ourselves."