Savannah Sparrows Changing Tunes Partly to Attract Females: Study
A new study finds that male savannah sparrows are changing their tunes, as a result of cultural evolution.
Researchers from Canada and the United States have found that the song of male savannah sparrows (Passerculus sandwichiensis) has changed drastically in the last 30 years (from 1980 to 2011), partly to attract the females.
For their study, the research team used sonograms to record songs of the male sparrows, living on Kent Island, N.B., in the Bay of Fundy, each breeding season for over 30 years. Male sparrows sing only one song type that consists of several parts. They learn the songs in their first year from their fathers or older male birds and continue to sing the same for the rest of their lives.
Although the birds sing the same verses and the sounds appear similar, each male sparrow has his own unique sound, said the researchers.
The research team noticed that the song has three primary elements. The first element identifies that the bird is a savannah sparrow, the second identifies which individual is singing, and the third component is used by females to assess males. Based on their analyses, the researchers found that the introductory notes of the songs had remained consistent for the last 30 years, but the sparrows had added a series of clicks to the middle of their songs. They also discovered that the ending trill (once long and high-frequency) has been changed to a shorter and lower frequency, as the males with shorter trills had higher reproductive success.
"The change is the result of cultural transmission of different song elements through many generations," Ryan Norris, Integrative biology professor from University of Guelph, Canada, said in a statement. "If you listen to how people used to talk in the 1890s and how we talk today, you would notice major differences, and this is the result of shifts in culture or the popularity of certain forms," he said. "The change in sparrow songs over time has occurred much the same way."
The details of the study appear in the January 2013 issue of Animal Behaviour.