Individual differences in song plasticity in response to social stimuli and singing position

Zebra finch song parameters are affected by the breeding status of the male, but not temperature variability

Bird song is a crucial feature for mate choice and reproduction. Song can potentially communicate information related to the quality of the mate, through song complexity, structure or finer changes in syllable characteristics. It has been shown in zebra finches that those characteristics can be affected by various factors including motivation, hormone levels or extreme temperature. However, although the literature on zebra finch song is substantial, some factors have been neglected. In this paper, we recorded male zebra finches in two breeding contexts (before and after pairing) and in two ambient temperature conditions (stable and variable) to see how those factors could influence song production. We found strong differences between the two breeding contexts: compared to their song before pairing, males that were paired had lower song rate, syllable consistency, frequency and entropy, while surprisingly the amplitude of their syllables increased. Temperature variability had an impact on the extent of these differences, but did not directly affect the song parameters that we measured. Our results describe for the first time how breeding status and temperature variability can affect zebra finch song, and give some new insights into the subtleties of the acoustic communication of this model species.

Using Acoustic Data Repositories to Study Vocal Responses to Playback in a Neotropical Songbird

Birds may alter song structure in response to territorial challenges to convey information about aggressive intent or fighting ability. Professional and amateur ornithologists upload daily many birdsong recordings into acoustic data repositories, usually scoring whether songs were recorded in response to a conspecific playback or produced spontaneously. We analyzed recordings from these repositories to evaluate if song traits of Rufous-browed Peppershrikes (Cyclarhis gujanensis) vary between playback-elicited songs and spontaneous songs. For each recording after playback, we chose one spatially closer spontaneous recording to avoid geographic bias. Birds recorded after playback produced slightly longer songs than birds that were singing spontaneously. This result was accounted for by increases in the amount of sound and silence within a song after the playback instead of changes in the mean number or duration of elements. Playback did not alter song frequency parameters (bandwidth, minimum, mean, and maximum frequencies) or song rate. These results indicate that song duration might mediate aggressive interactions in Rufous-browed Peppershrikes. Even considering limitations such as unknown playback stimulus identity and possible pseudoreplication, acoustic data repositories give a unique yet unexplored opportunity to gather insights into the evolution of song flexibility during aggressive encounters.

Urban Low-Rise Residential Areas Provide Preferred Song Post Sites for a Resident Songbird

Urbanization is expanding rapidly worldwide, and brings additional selection pressure on animals. The song differences between urban and rural songbirds have been widely verified, but the effects of urban morphological variation on long-settled urban birds have been poorly explored. Here, we investigated the distribution and song differences of a common resident songbird—the oriental magpie-robin (Copsychus saularis) between three urban morphology types (i.e., urban park, low-rise residential area, and high-rise residential area). The results indicated that the population density in low-rise residential areas was significantly higher than in urban parks, while it was the lowest in high-rise residential areas. Males in low-rise residential areas had greater song length, syllable numbers, frequency bandwidth, and song diversity than those in urban parks. The song differences were mainly related to habitat types, independent of singing height and perch type. Our findings suggest that low-rise residential areas may provide preferred song post sites for the oriental magpie-robin, which is well-adapted to the low-rise building morphology, but rejects the emerging high-rise buildings. Future studies are needed to assess the effects of urban morphological variation on more resident animals to determine which urban morphologies are conducive to enhancing biodiversity and encouraging animals to settle in urban areas.