This is Scientific American's 60-second Science, I'm Susanne Bard.Like many birds, male white-throated sparrows belt out songs to defend their territories and attract mates.And until the year 2000, one particular song stood out as the most popular white-throat tune in forests across Canada."The end part of the song is a three-syllable repeat. That's supposed to sound like 'Oh my sweet Canada, Canada, Canada.'"University of Northern British Columbia behavioral ecologist Ken Otter."And if you look in most books that describe what the song sounds like, it always has a three-syllable phrase at the end of it."But when Otter moved to Prince George, a wooded city in western Canada, 20 years ago, he noticed that its sparrows were singing a different tune."The males have dropped one of the notes, so instead of having three syllables repeating, it's actually two syllables repeating.""'Oh my sweet Cana, Cana, Canada.'"Back in the 1950s, though, the Prince George population was still singing the standard triplet song."So sometime during that 50-year period, the song had transitioned to this new dialect, and all the males had adopted it."Over the next few years, Otter's team discovered that the doublet song variant was spreading eastward."And it's replacing the old song as it goes."
这里是科学美国人――60秒科学系列，我是苏珊娜・巴德。“这首歌的结尾部分是三个音节的重复。听起来像是‘哦，我亲爱的加拿大，加拿大，加拿大。’”北不列颠哥伦比亚大学的行为生态学家肯・奥特说到。“如果你查阅描述这首歌的书籍，大多数都会说其结尾总有三音节的短语。”但20年前，在奥特尔到加拿大西部树木繁茂的城市乔治王子城时，他注意到那里的鸟儿唱着不同的曲调。“雄鸟漏掉了其中一个音符，因此歌曲结尾不是三个音节重复，而是两个音节重复。”“‘哦，我亲爱的加拿大，加拿大，加拿大。’”不过，上世纪50年代时，乔治王子城的鸟群仍在唱标准的三音节重复歌曲。“因此，在那50年中的某个时间，歌曲转变成这种新方言，所有的雄鸟都接受了这种方言。”之后几年，奥特的团队发现两音节重复歌曲的变体逐步向东传播。“它在传播过程中取代了老歌。”
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