Like Toucan Sam following his nose to Froot Loops, birds may use scent to find mates.

Though scientists have traditionally deemed odor insignificant in comparison to the wide array of colors, ornamentations, and calls of many avian mating displays, a team of researchers studying whether odor can predict reproductive success in birds discovered a striking correlation between smell and mate choice in dark-eyed juncos.

This new data could have potential implications for bird conservation research; “a junco is a basic songbird, which I never would have thought depended on smell in any way,” said Kim Peters, the Chief Scientist and Director of Bird Conservation at Mass Audubon, who was not involved with the study.

It could also influence studies on the olfactory systems of other species in which smell has not been considered noteworthy, and it may even suggest approaches for breeding programs and enrichment for birds in captivity as well, the researcher said.

The results were “surprisingly strong,” said Danielle Whittaker, the primary researcher and Managing Director of BEACON, the Center for the Study of Evolution in Action at Michigan State University.

Whittaker’s team analyzed a substance called preen oil, with which birds gloss their feathers daily and which contains a number of different chemicals (called volatile organic compounds, or VOCs) that make up a bird’s odor.

The researchers tested for certain compounds in preen oil that are known to increase during breeding season as the most likely culprits to influence mate choice.

They discovered a spectrum of these chemicals across the genders. While all of the birds’ oil had the same basic set of ingredients, the male juncos generally had a larger proportion of certain components in their oil, while the females generally had a larger proportion of other components, creating a range of more ‘male-like’ to more ‘female-like’ odor compositions.

They then found that both males with more ‘male-like’ odor compositions and females with more ‘female-like’ odors sired more offspring than the less ‘male’- or ‘female’- smelling of the genders, indicating that the compounds that make up a bird’s odor could be a reliable predictor of the number of offspring they produce.

The study also showed that more ‘female’-smelling males were more likely to be found helping raise chicks that were not genetically their own—a behavior called cuckolding.

For comparison, the researchers also tested visual traits that previous studies have shown to be attractive to females, including a higher percentage of white in their tail feathers and longer wing length. Whereas particular odor compositions correlated distinctly with higher number of offspring, neither wing length nor tail white showed a noticeable association with reproductive success, suggesting that, at least in this study, odor was a more reliable sign of attractiveness than these visual cues.

The study cautions that the discovered correlations most likely have underlying causes still to be discovered, and that much is yet unknown about chemical communication in birds and many other species as well. “This is a new field, and we’re learning new stuff every day,” said Whittaker.

As for humans and smell, little is currently known about the role of odor as well. According to Catherine Dulac, Professor of Molecular and Cellular Biology at Harvard, scent in humans is “[by] far not as important for reproduction as vision and sounds.”

Yet this study reveals that even for a species with seemingly more limited sensory experiences, “there is valuable information contained in odor,” Whittaker said; “all of the senses are important.”