Maturational changes in song sparrow song
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2022-01-01
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Abstract
Age-related changes in the production of sexually selected assessment signals have been identified across a diverse range of taxa, and in some cases, these changes have been shown to affect receiver response to those signals. One important type of change occurs even after a signaler reaches breeding age, a phenomenon known as delayed maturation. Delayed maturation has been observed in the songs of several bird species, with potential fitness consequences for males as a byproduct of female choosiness or male competition. Here, we analyzed songs recorded across the first three years of life in a cohort of hand-reared song sparrows Melospiza melodia to detect early-life age-related changes in song. We focused on three measures of song complexity, including within song type variation, the average number of notes and the number of unique note types for the most common variant of each song type, and five measures of song production patterns, including singing rate, time interval between songs within a bout of the same song type, time interval between bouts (i.e. when the song type changes), within-song stereotypy and between-song consistency. All measures of song complexity and most measures of song production patterns (excluding within-song stereotypy) changed significantly within individuals as birds aged from one to two years as well as from one to three years (excluding within-bout time interval), whereas no significant changes occurred from two to three years of age. Based on these features, a linear discriminant model could distinguish between the song of young (age 1) and older (age 2 and 3) adult males, providing support that song could serve as an indicator of age in this species. We discuss potential implications of these results for mate choice and male–male competition in song sparrows.
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Kochvar, KH, S Peters, MN Zipple and S Nowicki (2022). Maturational changes in song sparrow song. Journal of Avian Biology, 2022(1). 10.1111/jav.02872 Retrieved from https://hdl.handle.net/10161/26534.
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Stephen Nowicki
Our lab studies animal communication, asking both proximate and ultimate questions about how signaling systems function and how they evolve. Most of our work is done with birds, although lab members have studied a variety of other taxa. One major theme that runs through our work is to understand how signal reliability (“honesty”) is maintained in the face of the competing evolutionary interests of signal senders and receivers. We use both laboratory experiments and field-based analyses to test hypotheses about the costs of signal production, which theory suggests are necessary to maintain reliability. For example, we have demonstrated that the reliability of birdsong as a signal of quality in the context of mate choice is maintained by variation in the response of young birds to early developmental stress, which in turn affects brain development and song learning. Another theme that runs through our work concerns how animals themselves perceive signals, in particular the role of categorical perception in communication. Our work here began with birdsong, for example demonstrating context-dependent variation in category boundaries that define the smallest acoustic units of song (“notes”), and identifying categorical responses of neurons in the “song system” of the brain to variation in those notes. More recently, we have begun to study categorical perception in visual signaling, demonstrating for example that the carotenoid-based orange-red coloration commonly used in assessment signaling may be perceived categorically. This finding illustrates the connection between our interests in perception and reliability, given that canonical models of reliability assume continuous perception.
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