Reading the paper and the diagrams, I would say that the meaning of
frequency is purely Hertzian.
Cheers,
Carl Clifford
On 06/01/2011, at 11:15 AM, Philip Veerman wrote:
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
-----Original Message-----
From:
On Behalf Of Laurie Knight
Sent: Thursday, 6 January 2011 10:25 AM
Cc: Birding Aus
Subject: Urban silvereyes changing their tune
Actually, the article is freely available at
http://rspb.royalsocietypublishing.org/content/early/2011/01/05/rspb.201
0.2296.full
On 06/01/2011, at 9:19 AM, Laurie Knight wrote:
The abstract for the paper referred to in
http://www.theage.com.au/victoria/urban-songbirds-change-their-tune-2011
0105-19g94.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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