The activities are as follows:
- Teacher Guide
- Student activity, Graph Type A, Level 2
- Student activity, Graph Type B, Level 2
- Student activity, Graph Type C, Level 2
- Grading Rubric
Animals collect information about each other and the rest of the world using multiple senses, including sight, sound, and smell. They use this information to decide what to eat, where to live, and who to pick as a mate. Choosing a mate is an important decision that requires a lot of information, such as how healthy a potential partner is, and information about their genes. Mate quality can affect how many offspring an animal has and if their genes will get passed on to the next generation.
Many male birds have brightly colored feathers that are attractive to females. For example, the peacock has bright and elaborate tail feathers, called ornaments, which are thought to communicate a male’s quality. Besides using their sense of sight to see ornaments, female birds may use their other senses to gather information about potential mates as well. Danielle, a biologist, wanted to figure out if birds use vision and their other senses, such as smell, to determine the quality of potential mates.
Danielle decided to research how dark-eyed juncos communicate through their sense of sight and smell. Dark-eyed juncos, a type of sparrow, are not colorful birds like peacocks, but they have bright white feathers in their tails. Male dark-eyed juncos have more tail-white than females. Females may use the amount of white in a male’s tail to determine whether he is a high quality mate. Danielle was also interested in several chemical compounds found in junco preen oil, which birds spread on their feathers. This preen oil contains compounds that give birds their odor. Danielle found that males and females have different odors! Just as males have more white in their tail feathers, they also produce more of a chemical called 2-pentadecanone. Danielle wanted to test whether this chemical might be a signal of mate quality.
To test her two alternative hypotheses, Danielle captured male juncos at Mountain Lake Biological Station in Virginia. She measured their amount of tail-white by estimating the proportion of each tail feather that was white, and adding up the values from each feather. She also took preen oil samples and measured the percent of each sample that was made up of 2-pentadecanone. She followed these birds for one breeding season to find out how many offspring they had. If females pick mates based on visual ornaments, then she predicted males with more tail-white would have more offspring. If females pick mates based on smell, then she predicted males with more 2-pentadecanone would have more offspring.
Featured scientist: Danielle Whittaker from Michigan State University
To learn more about Danielle’s work with juncos, see her blog posts “The sweet smell of (reproductive) success” and “Deciphering avian aromas” on the BEACON website. To learn more about Danielle and her research, check out this episode from the PBS/NOVA webseries “The Secret Life of Scientists and Engineers” where she was featured.
There is a scientific paper associated with the data in this Data Nugget. The citation and PDF for the paper is below.
Whittaker, D., N.M. Gerlach, H.A. Soinic, M.V. Novotnyc, and E.D. Ketterson (2013) Bird odour predicts reproductive success. Animal Behaviour 86(4): 697-703