For over 30 years, scientists have been recording the songs of savanna sparrows on Kent Island, a small island just south of Grand Manan Island in the Bay of Fundy. After analyzing this vast collection of bird songs, integrative biology professors Ryan Norris and Amy Newman and their colleagues at Bowdoin College and Williams College have found that male savanna sparrows have adjusted their song to better attract females.
The research team found that savannah sparrows sing a song that consists of three components. The first component is common to all savannah sparrows. It's like a little jingle that identifies the singer as belonging to the species. The second component is unique to the individual bird that is singing. The third component is used by females to ascertain which males are likely to be the better mates.
Scientists noted that both the third component of the song, the one aimed at attracting females, has changed over the past three decades. They found that the trill that ends the song is now shorter and lower frequency than it had been in the past.
Photo © Rolf Nagel.
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