Songbirds with a Shared Olfactory Preference often Display Affinity Towards Each Other
In a groundbreaking discovery, a team of researchers led by Amber Rice, an associate professor of evolutionary biology at Lehigh University, has documented the preference of hybridizing songbirds for the scent of their own species. The study, titled "Conspecific olfactory preferences and interspecific divergence in odor cues in a chickadee hybrid zone," has been published in the journal Ecology and Evolution.
The research focused on the black-capped chickadee and the Carolina chickadee, two species that hybridize in the eastern Pennsylvania region. Previous studies have been limited in understanding the role of the sense of smell in birds, particularly songbirds, due to their impressive plumage and song variation. However, this new study sheds light on the importance of olfactory signaling in the reproductive isolation between these two closely related species.
The researchers found that both black-capped and Carolina chickadees produce chemically distinct natural oils. These unique chemical profiles, detected through olfaction, serve as species-specific scent signatures that help the birds distinguish conspecifics from heterospecifics. This discrimination reduces hybridization by guiding mate choice and social interactions preferentially toward conspecifics, thereby contributing to reproductive isolation despite geographic overlap.
The study also revealed that the black-capped and Carolina chickadees interbreed, but their hybrid offspring suffer fitness costs, such as lower hatching rates and lower cognitive abilities compared to pure-species birds. This further underscores the importance of maintaining species boundaries through olfactory communication.
Within the hybrid zone, the two species show differences in their uropygial oil chemistry. This finding could pave the way for future studies of songbird behavior, such as mate choice, predation risk assessment, or competitive interactions, to investigate odor as a factor.
The research was supported by the university, the National Science Foundation, the Society for the Study of Evolution (The Rosemary Grant Award), and the Animal Behavior Society. The team believes that their study will be of interest to researchers in the fields of animal behavior and chemical ecology.
Notably, this is the first example in currently hybridizing species that has been documented where species of songbird can smell and prefer their species' odors. The preferences for same-species odors are consistent with a possible role for olfactory signaling in premating reproductive isolation in chickadees.
In essence, Rice and her team's study provided evidence that olfactory signals function as an important pre-mating barrier, reinforcing species separation between these two chickadee species through chemical communication.
- The faculty of Lehigh University, led by Amber Rice, a member of the science department, has commenced a new research project focused on the black-capped chickadee and the Carolina chickadee, analyzing the role of olfaction in their mating behaviors and reproductive isolation.
- The researchers in this study investigating songbirds discovered that the distinct natural oils produced by both species serve as unique scent signatures, enabling the birds to recognize conspecifics from others, reducing hybridization rates and contributing to stronger species boundaries.
- Beyond understanding the preferences of hybridizing songbirds for their respective species' scents, this research emphasizes the importance of health-and-wellness factors like fitness and exercise in the reproductive success of songbirds, as the hybrid offspring were found to experience fitness costs compared to pure-species birds.
