The abstract for the paper referred to in http://www.theage.com.au/victoria/urban-songbirds-change-their-tune-20110105-19g94.html is as follows
Geographically pervasive effects of urban noise on frequency and syllable rate of songs and calls in silvereyes (Zosterops lateralis)
Dominique A. Potvin, Kirsten M. Parris and Raoul A. Mulder
Published online before print
Proc. R. Soc. B January 5, 2011, doi:10.1098/rspb.2010.2296
Abstract
Recent studies in the Northern Hemisphere have shown that songbirds living in noisy urban environments sing at higher frequencies than their rural counterparts. However, several aspects of this phenomenon remain poorly understood. These include the geographical scale over which such patterns occur (most studies have compared local populations), and whether they involve phenotypic plasticity or microevolutionary change. We conducted a field study of silvereye (Zosterops lateralis) vocalizations over more than 1 million km2 of urban and rural south-eastern Australia, and compared possible effects of urban noise on songs (which are learned) and contact calls (which are innate). Across 14 paired urban and rural populations, silvereyes consistently sang both songs and contact calls at higher frequencies in urban environments. Syllable rate (syllables per second) decreased in urban environments, consistent with the hypothesis that reflective structures degrade song and encourage longer intervals between syllables. This comprehensive study is, to our knowledge, the first to demonstrate varied adaptations of urban bird vocalizations over a vast geographical area, and to provide insight into the mechanism responsible for these changes. ===============================
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I wondered the same thing, but decided that it meant pitch, as they used the expression “sing at higher frequencies” rather than “sing with higher frequencies”.
Peter Shute
Reading the paper and the diagrams, I would say that the meaning of frequency is purely Hertzian.
Cheers,
Carl Clifford
Sort of sounds interesting. Do others see an unfortunate possible ambiguity here? In that “frequency” has two meanings of relevance. In this case by context it appears to mean how often something occurs in time, not the sound frequency, as in what we hear as pitch. But then again maybe it is both, in the same way that playing a tape faster raises the pitch………..
Philip
Actually, the article is freely available at http://rspb.royalsocietypublishing.org/content/early/2011/01/05/rspb.2010.2296.full
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