February 1, 2006 | David F. Coppedge

Birds Sing Duets

The little wrens in your backyard are not only soloists; they sing duets.  A number of birds have been found to sing together in unison, or in antiphonal pairs.  Some alternate melodic lines in rapid-fire succession and some sing in choirs.  This was described by Susan Milius in Science News.1  One ornithologist was stunned in the mists of Ecuador when he heard a group of wrens singing together, in “one of the most complex singing performances yet described in a nonhuman animal.”  Duetting is known in at least 222 species of birds.
    One researcher found a four-part, synchronized chorus with alternating parts of males and females who shifted parts at least twice a second.

And when one considers the split-second alternation, the birds’ singing surpasses human vocal virtuosity.
    That’s the latest, most extreme example of duetting birds, a phenomenon that has fascinated birders for decades and inspired its own chorus of theorizing about what might drive such displays.  Warning off rivals?  Foiling flirtations?  Checking musical passwords?  In the past few years, field biologists have applied modern ideas about evolution to begin new tests of why duetters do it….
Over several decades, scientists have offered at least a dozen explanations for the purpose of avian duets.  The theories have focused on the forest, the pair, or conflicts of interest between individual birds.
  (Emphasis added in all quotes.)

Milius listed a number of proposals, but each seems to have exceptions, and none rises to the top.  “All the ideas about the function of duets need more testing,” is the conclusion.  “As bird duets start to make sense, maybe they’ll shed light on other duetting species.  Birds duet.  Bugs duet.  Even some primates do it.” (That’s us.)
    The online article has links to websites where you can listen to sound files of the birds singing.  Here’s one by Mennill and Rogers and another from Daniel Mennill in Costa Rica.

1Susan Milius, “Just Duet: Biologists puzzle over bird’s ensemble vocalizations,” Science News, Week of Jan. 28, 2006; Vol. 169, No. 4 , p. 58.

It seems overkill for evolution to produce the complex brains and sensory capabilities required for high-speed coordinated singing of melodic lines just to protect territory or attract mates.  There are things in nature too wonderful for mere survival.

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Categories: Birds

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