Buzzwords in Females’ Ears? The Use of Buzz Songs in the Communication of Nightingales (Luscinia megarhynchos)

Abstract

Differences in individual male birds’ singing may serve as honest indicators of male quality in male-male competition and female mate choice. This has been shown e.g. for overall song output and repertoire size in many bird species. More recently, differences in structural song characteristics such as the performance of physically challenging song components were analysed in this regard. Here we show that buzz elements in the song of nightingales (Luscinia megarhynchos) hold the potential to serve as indicators of male quality and may therefore serve a communicative function. Buzzes were produced with considerable differences between males. The body weight of the males was correlated with one measure of these buzzes, namely the repetition rate of the buzz subunits, and individuals with larger repertoires sang buzzes at higher subunit-rates. A model of buzz performance constraints suggested that buzzes were sung with different proficiencies. In playback experiments, female nightingales showed more active behaviour when hearing buzz songs. The results support the idea that performance differences in the acoustic fine structure of song components are used in the communication of a large repertoire species such as the nightingale.

What is the whistle all about? A study on whistle songs, related male characteristics, and female song preferences in common nightingales

“…No female showed copulation solicitation displays in this or other playback experiments (see Weiss et al 2012), regardless of whether they were treated with estradiol or not. Thus, we used other behavioural parameters to assess female responses to the different song qualities.…”

“…Five females were implanted subcutaneously (skin covering the breast muscle) with an estradiol pellet. The four remaining females were treated the same, but received only a sham-implant (pellets composed of pure Silastic adhesive without estradiol; for details on estradiol treatment, see Weiss et al 2012). During playbacks, the data of two females were lost due to technical failure of the recording equipment in the sham-implanted group.…”

“…To determine general behavioural activity, we counted the number of location changes within the cage (including hops between perches or at the ground and flights) and the number of tail lifts. These parameters have been used as proxy for female song preferences before (Baker 1983;Caro et al 2010;Weiss et al 2012). Also, we counted the number of vocalizations emitted by females (e.g., short calls like ''huit'' and ''karr'', Glutz von Blotzheim and Bauer 1989; Kipper et al 2014) during each treatment to further evaluate female song responsiveness.…”

“…Considering the numerous different song types, different song categories have been identified in nightingale singing (whistle song : Hultsch 1980;Naguib et al 2002;trill song: Kunc et al 2006trill song: Kunc et al , 2007buzz song: Weiss et al 2012). The only direct evidence that categories are meaningful to females as well was provided for buzz songs (Weiss et al 2012). Another song category, the whistle song, has long been hypothesized to play a role in mating (Hultsch 1980).…”

“…These responses include behaviours that are clearly associated with sexual contexts, such as copulation solicitation displays (CSD), or more subtle behaviours such as postures, movements, or calls that indicate increased activity and female arousal (Searcy 1992b). To date, only one study reported an experimental test of song preferences in nightingales (Weiss et al 2012). According to this study, we expected more location changes and certain postures in response to whistle song playbacks.…”