Stephanie M. Topp and Daniel J. Mennill (2008): Seasonal variation in the
duetting behaviour of rufous-and-white wrens ( Thryothorus rufalbus ).
Behav. Ecol. Sciobiol. 62(7), 1107-1117.
Abstract: Seasonal variation in animal signalling behaviour has been well
documented and has contributed much to our understanding of male signals. In
contrast, we know little about seasonal variation in female signals or
signals produced jointly by males and females, such as the vocal duets of
birds. Here, we examine how singing behaviour changes in relation to time of
year and breeding stage in rufous-and-white wrens (Thryothorus rufalbus),
neotropical songbirds where both males and females sing and where breeding
partners coordinate songs to produce vocal duets. We recorded a
colour-marked population of birds over an extended time period encompassing
multiple breeding stages. Across all time frames and breeding stages, males
sang at higher rates than females and male solos were more common than duets
or female solos. Males and females showed divergent seasonal patterns of
singing. Females sang more often early in the year, during the pre-breeding
season, and female song tapered off as the breeding season progressed.
Duetting followed a parallel pattern, which resulted from females showing
less duet responsiveness to their partner's songs later in the year. Male
independent song rate peaked at the onset of the rainy season - a time when
females become fertile - and males showed the highest level of duet
responsiveness during this period. Our results suggest that early in the
year, duets appear to be cooperative displays, functioning in joint
territory defence and/or the coordination of breeding activities. When
females are fertile, however, increased duet responsiveness by males is
consistent with mate or paternity guarding.
URL: http://www.springerlink.com/content/l602224vj4315305/
For reprints please contact Daniel J. Mennill (Email:
Mark E. Laidre and Sandra L. Vehrencamp (2008): Is bird song a reliable
signal of aggressive intent? Behav. Ecol. Sciobiol. 62(7), 1207-1211.
Abstract: In this commentary, we discuss recent experiments on the
reliability of bird song as a signal of aggressive intent during territorial
conflicts. We outline relevant theoretical views on honest signaling,
highlighting the vulnerability handicap hypothesis as a possible explanation
for soft song's reliability in predicting attack. We also sketch possible
methods of testing whether soft song agrees with key predictions of the
vulnerability handicap hypothesis. Finally, we suggest possible empirical
refinements that may be useful in future studies of signals of intent, both
in birds and in animals broadly. In particular, we argue that future studies
of intent should strive to incorporate the following elements into their
experimental design: (1) multi-modal signal components, (2) interaction
dynamics, and (3) minimal time intervals. Simulated exchanges using
dynamically interactive models may provide a powerful means of incorporating
all three of these design features simultaneously.
URL: http://www.springerlink.com/content/p2055358l1k61052/
For reprints please contact Mark E. Laidre (Email:
Kind regards
Sonja Amoser
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Dr. Sonja Amoser
Daringergasse 3
1190 Wien
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