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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2009.04.028 Byline: Douglas A. Nelson, Angelika Poesel Abstract: Song learning in birds makes it possible for males to faithfully imitate tutors and also to generate novel improvisations. Within local dialects of the Puget Sound white-crowned sparrow, most males share the terminal trill phrase in their songs. In contrast, the introductory note complex is more variable within local populations and appears to encode individual identity. We studied the song-learning process during initial territory establishment in a wild population of white-crowned sparrows. Although most adult males sing a single song type, many yearling males overproduce song types early in their first singing season before deleting all but one song type from their repertoire. We asked whether this attrition process favours retention of a song with a note complex that resembles that of a male's neighbour, as would be predicted by various hypotheses assuming a benefit to song sharing, or whether it favours retention of a distinctive note complex, which would produce individuality in song. We found that males that initially overproduced song types retained shared note complexes, and that these males were more likely to share their adult note complex with neighbours than were young males that did not overproduce. Only 51% of recruits overproduced, however, and we close by speculating that overproduction and close song sharing may be correlates of male quality and learning ability. Author Affiliation: Borror Laboratory of Bioacoustics, Department of Evolution, Ecology and Organismal Biology, The Ohio State University, U.S.A. Article History: Received 6 January 2009; Revised 2 March 2009; Accepted 23 April 2009 Article Note: (miscellaneous) MS. number: A09-00016

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2007.01.018 Byline: Douglas A. Nelson, Angelika Poesel Abstract: Many bird songs are highly complex acoustic signals that broadcast a variety of information over long distances. General explanations for signal complexity assume that either different signal components are redundant, or that each component conveys a different message. Puget Sound white-crowned sparrow, Zonotrichia leucophrys pugetensis, song consists of several temporally discrete phrases or components, two of which, the note complex and trill, vary independently across vocal dialects. Previous playback experiments with males suggest that the terminal trill encodes dialect identity. Here we test whether both the note complex and trill encode individual identity, as predicted by the redundancy hypothesis, or whether the note complex alone serves this role, as predicted by the multiple messages hypothesis. Analyses of acoustic variation in note complexes and trills, and results of a neighbour-stranger song discrimination playback experiment support the multiple messages hypothesis. Note complexes were more individually distinctive among males, and males responded stronger when a neighbour's song had a stranger's note complex substituted than when the neighbour's trill was replaced with that of a stranger. The segregation of cues to individual and dialect identity into the note complex and trill phrases, respectively, supports the hypothesis that coding conflicts may be resolved by using different song components for different functions. Author Affiliation: Borror Laboratory of Bioacoustics, Department of Evolution, Ecology and Organismal Biology, The Ohio State University, U.S.A. Article History: Received 6 October 2006; Revised 27 November 2006; Accepted 15 January 2007 Article Note: (miscellaneous) MS. number: A10584

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2005.10.022 Byline: Angelika Poesel, Hansjoerg P. Kunc, Katharina Foerster, Arild Johnsen, Bart Kempenaers Abstract: Sexual selection theory predicts that signals reflecting the relative quality of individuals should be used in mate choice. Females could base their choice of copulation partners on male secondary sexual traits that honestly signal male age, as predicted by the age-based indicator mechanism. Studies have shown that female blue tits prefer older males and that aspects of dawn song reflect male quality, but it remains unknown whether dawn song characteristics correlate with male age. We compared dawn song characteristics of second-year (SY) and older (ASY) male blue tits (cross-sectional analysis), and tested for age-related changes within individuals (longitudinal analysis) and differential overwinter survival of SY males. We further investigated the relation between dawn song and paternity gain and loss. We found that ASY male blue tits began to sing earlier relative to sunrise than did SY males. This difference in the onset of dawn singing was due to age-related changes in individual performance rather than differential survival of individuals with varying expression of the trait. Males that began to sing earlier at dawn had more mating partners, and were more likely to gain extrapair paternity. Our findings suggest that the onset of dawn song can provide a simple mechanism for females to assess the relative quality of their mate and of neighbouring males. We propose that females use the onset of singing as a cue for their choice of extrapair partners. Author Affiliation: (a) Animal Behaviour Group, Biological Institute, University of Copenhagen, Denmark (a ) Department of Animal Behaviour, University of Bielefeld, Germany (a ) Max Planck Institute for Ornithology, Germany (As.) Natural History Museum, University of Oslo, Norway Article History: Received 17 September 2004; Revised 4 December 2004; Accepted 20 October 2005 Article Note: (miscellaneous) MS. number: 8280R

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2005.04.004 Byline: Angelika Poesel, Torben Dabelsteen Abstract: Territorial songbirds frequently challenge each other with intrusions and close-range singing interactions. The timing of songs in such interactions may signal aggressive intentions and experiments have shown that song overlapping may indicate a higher willingness to escalate an interaction than song alternating. A territory owner should therefore perceive an intruder overlapping its songs and staying inside its territory as a greater threat than one alternating and exiting the territory quickly. To test this hypothesis we used playback to interact with territorial male blue tits, Parus caeruleus, by varying the amount of overlap of a subject's song; we also used multiple loudspeakers to simulate an intruder changing song posts. The territory owners approached and followed simulated intruders that changed song post inside their territories more slowly when more of their songs had been overlapped at the first loudspeaker, and they did not follow an intruder outside their territory. Nevertheless their responses remained high throughout playback and interaction terms between proportion of songs overlapped and loudspeaker position inside or outside the territory indicated that male blue tits combined and used information from both singing and intrusion patterns. Author Affiliation: Animal Behaviour Group, Biological Institute, University of Copenhagen, Denmark Article History: Received 11 March 2004; Revised 26 April 2004; Accepted 3 April 2005 Article Note: (miscellaneous) MS. number: 8047R

Bird song has the potential to convey a variety of information about the singer, including the singer's current motivational state. A recent review by Searcy & Beecher (2009) (Anim. Behav. 78, 2009; 1281) emphasized how little is currently known about whether song functions as an aggressive signal in territorial interactions. A recent observational study of song length variation in the Puget Sound white-crowned sparrow reported that males shorten the terminal trill in their single song type while singing close by another male, and shorten the trill even further immediately before chasing the opponent. Here, we report the results of two song playback experiments designed to test whether males distinguish the differences in song length that occur in agonistic and non-agonistic contexts. We found that males gave stronger responses, as measured by close approach distances, to either a series of songs increasing in duration (compared to a series decreasing in duration), or to long loud songs (compared to short soft songs). In both experiments, males gave weaker responses to the stimuli hypothesized to be more aggressive. Males shortened their songs in response to both simulated intrusions. Combined with the observational data on song variation in different contexts, these experiments support the conclusion that song length variation contains information about aggressive motivation in the white-crowned sparrow. [ABSTRACT FROM AUTHOR]

Signals of closely related species tend to be more distinct when occurring in sympatry than in allopatry. Such differences allow species-specific identification and presumably reduce interspecific mating. Among chickadees, dawn chorus behaviour affects female mate choice. Within our sympatric study population of black-capped chickadees, Poecile atricapillus, and mountain chickadees, Poecile gambeli, directional hybridization occurs via extrapair matings between female mountain chickadees (the subordinate species) and male black-capped chickadees (the dominant species). In this study, we compared dawn singing from this sympatric population with dawn recordings from allopatric populations of each species. Mountain chickadees used more chick-a-dee calls than songs during the dawn chorus when they co-occurred with black-capped chickadees in the sympatric population, but used similar proportions of calls and songs in the allopatric populations. We also found differences in the fine structure of the song; both species typically had a descending first note in their song (glissando), but mountain chickadees in the sympatric population used an ascending first note. The internote ratio between the first two notes of the song of the sympatric mountain chickadees lacked a characteristic frequency drop found in the allopatric mountain chickadee population and in the allopatric and sympatric populations of black-capped chickadees. Geographical analysis of songs of mountain chickadees across western North America revealed consistent differences in song features among sympatric/allopatric populations in different regions, but the nature of character shifts were not always parallel among populations. These findings illustrate possible character displacement in a subordinate species (mountain chickadee) to reduce acoustic overlap with a dominant heterospecific (black-capped chickadee). [ABSTRACT FROM AUTHOR]