Elizabeth Derryberry, a biologist at Duke University in North Carolina, compared recordings of sparrow hits from 1979 to those of 2003 and found that the newer songs have a much slower rhythm and dip further down into the lower registers. And upon playing the different versions to hip, modern-day sparrows in a variety of areas, she found that today's birds are much more into current chart hits than those of 30 years ago.
The 20 males that heard Derryberry's two recordings reacted much more aggressively to the new tunes, ready to defend their territory against the crooning interloper. And the chicks? They responded by becoming more open to sexual advances when the new music was played. The oldies didn't turn them on at all.
"I'm not saying a female bird won't respond to an old song, but not as much as she would to the newer version," Derryberry told the newspaper the Daily Telegraph. "They regard the old songs as not as interesting, not as good as the new ones."
The scientist, who carried out her experiment near Yosemite National Park in California, has been studying bird song recordings made over the last three decades to determine how tunes evolve and whether the changes have to do with mate selection or habitat. The results of her test, she says, show that stylistic differences develop rather quickly, affecting mating and the passing on of genetic information. It could even provide clues to how new species develop.
Regional dialects among songbirds have long been recognized, as has the fact that birds -- like humans -- respond more strongly to local songs than to those from abroad. However scientists were previously less knowledgeable about changes over time.
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