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First published online January 12, 2004
Journal of Experimental Biology 207, 567 (2004)
Copyright © 2004 The Company of Biologists Limited
doi: 10.1242/jeb.00827
Inside JEB |
FINCHES' BIG BEAKS TRIM TRILLS
kathryn{at}biologists.com
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Although the beaks of Darwin's finches have been credited with inspiring the theory of natural selection, it took Darwin almost a year to realise that the tiny birds were all members of the same family and that their intriguingly shaped beaks had evolved in response to their island's ecology. But how do these bird's diverse beak morphologies affect the songs they sing? Jeffrey Podos, Joel Southall and Marcos Rossi-Santos wondered whether the finches adjusted their beak gapes while singing, to adjust the pitch of their whistles, regardless of their beak's build (p. 607).
Filming seven finch species as they serenaded on the Galápagos Islands, Podos and his colleagues analysed the opening beaks, and looked for a correlation with the frequency of the bird's trills. The team found that as the birds hit high notes they threw their beaks wider than when chirruping a low note, regardless of whether they had dainty insect plucking beaks or thickset nut crushers. They add that as birds with larger beaks cannot open them as fast as daintier beaked species, birds with large beaks have evolved songs that trill at a relatively low rate to produce less complex songs, to match their beak's reduced agility. So no matter what their shape, Darwin's finch's all use their beaks in the same ways to enhance their tones.
References
Podos, J., Southall, J. A. and Rossi-Santos, M. R.
(2004). Vocal mechanics in Darwin's finches: correlation of beak
gape and song frequency. J. Exp. Biol.
207,607
-619.
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