A review of acoustic playback techniques for studying avian vocal duets

Abstract

Playback experiments involve the broadcast of natural or synthetic sound stimuli and provide a powerful tool for studying acoustic communication in birds. Playback is a valuable technique for exploring vocal duetting behavior because it allows investigators to test predictions of the various hypotheses for duet function. Here, we adopt a methodological perspective by considering various challenges specific to studying duetting behavior, and highlighting the utility of different playback designs for testing duet function. Single‐speaker playback experiments allow investigators to determine how duetting birds react to different stimuli, but do not simulate duets in a spatially realistic manner. Multi‐speaker playback experiments are superior to single‐speaker designs because duet stimuli are broadcast with spatial realism and unique and additional predictions can be generated for testing duet function. In particular, multi‐speaker playback allows investigators to evaluate how birds respond to male versus female duet contributions separately, based on reactions to the different loudspeakers. Interactive playback allows investigators to ask questions about the time‐ and pattern‐specific singing behavior of birds, and to understand how singing strategies correspond to physical behavior during vocal interactions. Although logistically challenging, interactive playback provides a powerful tool for examining specific elements of duets (such as the degree of coordination) and may permit greater insight into their functions from an operational perspective. Interactive playback designs where the investigator simulates half of a duet may be used to describe and investigate the function of pair‐specific and population‐wide duet codes. Regardless of experimental design, all playback experiments should be based on a sound understanding of the natural duetting behavior of the species of interest, and should aim to produce realistic and carefully controlled duet simulations. Future studies that couple playback techniques with other experimental procedures, such as Acoustic Location System recordings for monitoring the position of birds in dense vegetation or multimodal techniques that combine acoustic with visual stimuli, are expected to provide an even better understanding of these highly complex vocal displays.

Low Levels of Extra-Pair Paternity in a Neotropical Duetting Songbird, the Rufous-and-white Wren (Thryothorus rufalbus)

“…These complex acoustic displays occur when two birds, usually the male and female of a mated pair, combine their vocalizations in a coordinated fashion (Farabaugh 1982, Hall 2004, 2009, Douglas and Mennill 2010. Few studies have determined the genetic mating strategy of tropical duetting species, so it is not yet possible to assess the relationship between duetting behavior and genetic mating strategy accurately.…”

Analyses of sex and individual differences in vocalizations of Australasian gannets using a dynamic time warping algorithm

“…Extensive analyses of vocalizations recorded from our sample of Australasian gannets demonstrate that these birds have a complex repertoire of call elements that are both consistent in structure and variable across different scales of biological levels. Some call elements were observed to coincide with certain behaviors; however, more focused studies observing and experimentally addressing the role of behavioral contexts on call element use-patterns in this species would be required in the future to confirm this (Douglas and Mennill, 2010), as it was not the focus of this study.…”

Female happy wrens select songs to cooperate with their mates rather than confront intruders

“…We used a two-speaker design [14], consisting of a wireless playback speaker (FoxPro GX-7) connected by a 10 m cable to a second speaker (FoxPro SP-55; frequency responses: 40 Hz-22 kHz). Each speaker played one channel of the two-channel recording, and (a,b) Natural duets produced by focal pairs were used to create (c) 2-channel playback stimuli by inserting female songs from one duet followed by male songs from the other duet.…”