Biology Reference
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White-necked Thrush
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Cocoa Thrush
Time (s)
Fig. 3.6 Spectrogram of the white-necked thrush and cocoa thrush that illustrates well the
difference in syllable structure (Reproduced with permission from Nemeth et al. 2006 )
suggest the role of phenotypic plasticity is incorporated in the connection between
environmental structure and individual call attributes (Fig. 3.7 ). In nature, animals
living in a natural noisy background such as a stream adopt this strategy, as does the
dipper Cinclus mexicanus (Kingery 1996 )or Phylloscopus magnirostris (Dubois
and Martens 1984 ), which have sound repertoires quite distinct from other bird
species living in quieter habitats.
Boeckle et al. ( 2009 ) have found that the skipper frog ( Staurois latopalmatus )
that lives along the waterfalls of Bornean streams has a sound repertoire well
adapted to this exclusive environment. In fact, this species seems to avoid quiet
stream environments. This frog has two types of calls, a short single-note and a long
multi-note call. Both calls have a sound pressure that is less than the noise produced
by a waterfall. The dominant frequency is around 5 kHz, and from the correlation
between the body size (snout-vent length) of 74 Ranidae and their dominant
frequency it appeared that this species should have a lower frequency, and
the results suggest an acoustic adaptation to a low-frequency-dominated noise.
These authors suggest that microhabitat characteristics can act as a strong selective
pressure on the patterns of the acoustic signals.
There are increasing evidences that body and bill size, associated with habitat
structure, influence the communication mechanism, at least in birds. Recently
Derryberry ( 2009 ) focused on the variation of trills in the white-crowned sparrow
( Zonotrichia leucophrys ). Trills that are repetitions of the same syllable seem more
affected by the mechanisms of sound production and by habitat-dependent selec-
tion. Reverberation, defined as the amount of energy residual from a note and
reverberated by the vegetation or other objects that fill the silent interval between
notes, affects the transmission of frequency-modulated trills. Vegetation density,
transmission distance, frequency, element repetition rate, and element position
within the trills are factors influencing the reverberation effect. In dense vegetation
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