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: [EMAIL PROTECTED]) 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: [EMAIL PROTECTED]) Kind regards Sonja Amoser ************************** Dr. Sonja Amoser Daringergasse 3 1190 Wien [EMAIL PROTECTED]
