I found this in one of the birding mags I got recently think is
fascinating, close to my heart!
To humans a good singer has sex appeal and apparently the same is true
for some songbirds. Researchers at Duke University believe that female
swamp sparrows are most receptive to males who can sing difficult songs
(Can't say I like rap music though!)
To prove their claim, they first had to figure out how to identify a
good singer, a subjective task even among humans!
A break-through came when they noticed that the songs that male sparrows
sing vary in a predictable manner. Those songs that contained rapid
trills have few additional syllables that expanded across a broad range
of frequencies. More precisely, a male's vocal tract and neural control
don't allow singing of broadband trills! As a consequence, when singing
broadband syllables or notes he must forego rapid trills. It's a trade
off that researchers were interested in exploring.
This relationship was quantified by plotting trill rate against
frequency bandwidth on a two-dimensional graph. On such a graph, the
researchers statistically connected the dots representing the songs near
the top margins to arrive at the upper limit of a male's ability to
sing, at least in principle!
It was evident from field work that some males sing more "High
performance" songs than other males.
At this point, researchers became interested in determining if females
took notice when a male sang a difficult song! Apparently they do (what
taste) Females that were played these songs responded by giving a more
solicitation displays (9 out of 10 females were tested in this) than
when they were played "low performance" versions of the same song....
Who said birds had no taste?
Martyn
http://naturesound.org=20=20
http://groups.yahoo.com/group/Naturesound/
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