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(Abstracts below)
Radford, AN (2004) Voice breaking in males results in sexual dimorphism of
green woodhoopoe calls. Behaviour 141: 555-569.
Pasteau, M, L Nagle & M Kreutzer (2004) Preferences and predispositions for
intra-syllabic diversity in female canaries (Serinus canaria). Behaviour
141: 571-583.
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- Abstracts -
Radford, AN (2004) Voice breaking in males results in sexual dimorphism of
green woodhoopoe calls. Behaviour 141: 555-569.
Abstract: Ontogenetic changes and sexual differences in the acoustic
structure of green woodhoopoe (Phoeniculus purpureus) 'kek' calls were
investigated in a wild population. At fledging, the calls of males and
females were indistinguishable in terms of fundamental frequency, frequency
modulation, peak frequency and call duration. After 3-5 months, however, the
male voice 'broke' (i.e. underwent a significant decrease in fundamental
frequency), while there was no change in female call structure.
Consequently, the fundamental frequency of adult male calls was 48% lower
than that of adult females, and there was no overlap in the call frequencies
of the sexes in adulthood. The change in male voice occurred within a 23
week period and no intermediate call frequencies were recorded. The timing
of the voice break did not correspond with a change in overall body size,
suggesting that growth of the syrinx was not the proximate cause. However,
it did coincide with the stage in development when male bill length grew to
exceed that of all females and when males began to lose their distinctive
brown throat patch, providing some indirect evidence that hormonal control
may be important.
Pasteau, M, L Nagle & M Kreutzer (2004) Preferences and predispositions for
intra-syllabic diversity in female canaries (Serinus canaria). Behaviour
141: 571-583.
Abstract: The aim of this study is to examine the preferences of female
canaries for a particular cue in male song: the intra-syllabic diversity
(number and form of notes constituting a syllable) and to test both the role
of predispositions and of song experience in the development of these
preferences. Two groups of females were used. The first consisted of adult
females raised in acoustic isolation without song males experiences (ISO
group); the second, of song experienced adult females raised with singing
male in an aviary (AVI group). Female preferences for intra-syllabic
diversity were evaluated using the behavioral index of copulation
solicitation displays (CSD). Five different types of songs were tested:
three were made up of poor intra-syllabic diversity and two were made up of
great intra-syllabic diversity. The results demonstrate that, in each group
(AVI and ISO), intra-syllabic diversity is preferred to intrasyllabic
simplicity. In addition, the inter-group comparison showed no significant
differences between the two groups. In the aviary group, song learning by
sexual and sound experience did not seem to modify or influence the
intra-syllabic diversity preferences. Thus, female preferences for such a
diversity would result from early predispositions that are maintained in
adulthood.
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