A Duke researcher has found that what guys in a cappella groups have always known--a sweet song gets the girl.
At least for songbirds, that is.
According to the new study led by Professor of Biology Stephen Nowicki, songbirds may provide a major clue into the mechanisms of human learning and culture. The research, published in the Sept. 22 issue of Proceedings of the Royal Society: Biological Sciences, is the first to demonstrate that a male songbird's song performance affects the female bird's mating response. Previous studies had only shown that the absence of song or size of the repertoire influenced sexual success.
To determine the effect of fine differences in song quality, the researchers exposed captive-raised birds to recordings of wild birds and quantitatively measured how well each one copied the songs they heard. The scientists then exposed recently-captured female birds to the captive male birds' songs, and measured the sexual reaction by the number of times the female birds performed characteristic mating responses��such as wing shivering and specific calls.
"What we found is that females showed an overwhelming response to well-learned songs," Nowicki said. "We know that in many species of birds, females choose males based on their songs, but the reason why is a long-standing puzzle."
The solution to that puzzle now appears to lie in brain function��attaining a brain adept at song-learning is achieved by both successful early development and maintaining good health, explained Nowicki. Bird songs are thus a way for female birds to identify smart, healthy mates. "Brain development is directly linked to males' ability to sing songs well," Nowicki said. "What [a female bird] is really interested in is how well [a male bird] builds his brain."
Animals typically choose mates based on physical characteristics; peacock feathers and moose antlers are common examples. Physical strength, demonstrated by vocal capacity, also plays a role in avian sexual selection. Since birds are so small and singing requires a tremendous amount of energy, their songs often resemble a lion's roar.
The birds' emphasis on mental prowess for their mates puts them in very select company. "I know of no other example outside of humans and birds where animals select in this way," said Richard Mooney, associate professor of neurobiology at the Medical Center and an expert on the neurophysiology of song-learning.
Because of this link, researchers hope to gain insight into human behavior by studying birds, one of the only animals outside of humans that vocalize. "[Birds] learn like we do, by listening to a model and copying it. That's why they're so studied," Mooney said. "It gives us the potential to address what cellular mechanisms are involved in learning."
Mooney also noted the value of applying bird research to an understanding of human culture. "It speaks to the neurobiology of aesthetics--why do we consider some things as beautiful and not others? That may have a basis in sexual selection," he said. "To communicate is an art form. Humans have been strongly selected for [speech]."
Erich Jarvis, assistant professor of neurobiology and an expert on the evolution of vocal behavior, explained that bird research using molecular biology focuses on three types of questions.
"What are the genes that regulate vocal learning in the brain, how did brain pathways for vocal learning evolve and what can we learn about general brain function and how the brain works from examining vocal-learning birds?" Jarvis wrote in an e-mail.
Jarvis and Mooney have shown in past research that several species of birds have independently developed very similar brain structures used for song. Their current aim is to link this research to the development of human language.
Nowicki cautioned, however, that culture is a very mediating influence in our species. "It's very hard to generalize mate choice in animals to humans," he said.
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