Species-Specific Responses of Bird Song Output in the Presence of Drones

Drones are now widely used to study wildlife, but their application in the study of bioacoustics is limited. Drones can be used to collect data on bird vocalizations, but an ongoing concern is that noise from drones could change bird vocalization behavior. To test for behavioral impact, we conducted an experiment using 30 sound localization arrays to track the song output of 7 songbird species before, during, and after a 3 min flight of a small quadcopter drone hovering 48 m above ground level. We analyzed 8303 song bouts, of which 2285, from 184 individual birds were within 50 m of the array centers. We used linear mixed effect models to assess whether patterns in bird song output could be attributed to the drone’s presence. We found no evidence of any effect of the drone on five species: American Robin Turdus migratorius, Common Yellowthroat Geothlypis trichas, Field Sparrow Spizella pusilla, Song Sparrow Melospiza melodia, and Indigo Bunting Passerina cyanea. However, we found a substantial decrease in Yellow Warbler Setophaga petechia song detections during the 3 min drone hover; there was an 81% drop in detections in the third minute (Wald test, p < 0.001) compared with before the drone’s introduction. By contrast, the number of singing Northern Cardinal Cardinalis cardinalis increased when the drone was overhead and remained almost five-fold higher for 4 min after the drone departed (p < 0.001). Further, we found an increase in cardinal contact/alarm calls when the drone was overhead, with the elevated calling rate lasting for 2 min after the drone departed (p < 0.001). Our study suggests that the responses of songbirds to drones may be species-specific, an important consideration when proposing the use of drones in avian studies. We note that recent advances in drone technology have resulted in much quieter drones, which makes us hopeful that the impact that we detected could be greatly reduced.

Evidence for cumulative cultural evolution in bird song

In studies of cumulative cultural evolution in non-human animals, the focus is most often on incremental changes that increase the efficacy of an existing form of socially learned behaviour, such as the refinement of migratory pathways. In this paper, we compare the songs of different species to describe patterns of evolution in the acoustic structure of bird songs, and explore the question of what building blocks might underlie cumulative cultural evolution of bird song using a comparative approach. We suggest that three steps occurred: first, imitation of independent sounds, or notes, via social learning; second, the formation of categories of note types; and third, assembling note types into sequences with defined structures. Simple sequences can then be repeated to form simple songs or concatenated with other sequences to form segmented songs, increasing complexity. Variant forms of both the notes and the sequencing rules may then arise due to copy errors and innovation. Some variants may become established in the population because of learning biases or selection, increasing signal efficiency, or because of cultural drift. Cumulative cultural evolution of bird songs thus arises from cognitive processes such as vocal imitation, categorization during memorization and learning biases applied to basic acoustic building blocks. This article is part of a discussion meeting issue ‘The emergence of collective knowledge and cumulative culture in animals, humans and machines’.

Mitochondria as the powerhouses of sexual selection: testing mechanistic links between development, cellular respiration, and bird song

Although the influence of developmental conditions on the expression of sexually selected traits is established, the physiological mechanisms that modulate such effects remain a matter of intense debate. Here, we test the role of the developmental environment in shaping adult mitochondrial function and link mitochondrial function to expression of a sexually selected trait in males (bird song). We exposed male zebra finches (Taeniopygia guttata) to corticosterone (CORT) treatment during development. After males reached adulthood, we quantified mitochondrial function from whole red blood cells and measured baseline CORT and testosterone levels, body condition/composition, and song structure. CORT-treated males had less efficient mitochondrial function (FCRL/R), lower mitochondrial ‘working pace’ (FCRR/ETS), and higher baseline levels of CORT as adults compared to control males. Using structural equation modelling, we found that the effects of CORT treatment during development on adult mitochondrial function were indirect and modulated by baseline CORT levels, which are programmed by CORT treatment during development. Developmental treatment had an indirect effect on song peak frequency. Males treated with CORT during development sang songs with higher peak frequency than control males, but this effect was modulated through increased CORT levels and decreased mitochondrial efficiency (FCRL/R). CORT-treated males had smaller tarsi compared to control males; however, there were no associations between body size and measures of song frequency. Here, we provide the first evidence supporting links between the developmental environment, mitochondrial function, and the expression of a sexually selected display (bird song).

Punctuated evolution in the learned songs of African sunbirds

Learned traits are thought to be subject to different evolutionary dynamics than other phenotypes, but their evolutionary tempo and mode has received little attention. Learned bird song has been thought to be subject to rapid and constant evolution. However, we know little about the evolutionary modes of learned song divergence over long timescales. Here, we provide evidence that aspects of the territorial songs of Eastern Afromontane sky island sunbirds Cinnyris evolve in a punctuated fashion, with periods of stasis of the order of hundreds of thousands of years or more, broken up by evolutionary pulses. Stasis in learned songs is inconsistent with learned traits being subject to constant or frequent change, as would be expected if selection does not constrain song phenotypes over evolutionary timescales. Learned song may instead follow a process resembling peak shifts on adaptive landscapes. While much research has focused on the potential for rapid evolution in bird song, our results suggest that selection can tightly constrain the evolution of learned songs over long timescales. More broadly, these results demonstrate that some aspects of highly variable, plastic traits can exhibit punctuated evolution, with stasis over long time periods.

Synaesthetic Sanctuary

<p><b>Traditional scientific methods of visualising sound data have focused on techniques that attempt to capture distinct elements of the audio signal, such as volume and length. However, existing methods such as spectrograms and waveform analysis are limited in their expression of the characteristics associated with complex sounds such as bird song. This research explores strategies to visualise sound in an aesthetically engaging manner. It uses sound data from native New Zealand birds as a design tool for creating an audio-visual design system. The distinct focus on timing and pitch within these songs makes the data suitable for visual comparison. The design techniques explored throughout this research project attempt to express the unique characteristics of a variety of New Zealand bird songs and calls. It investigates how artistic audio-visual methods can be integrated with scientific techniques so that the auditory data can be made more accessible to non-specialists.</b></p> <p>More specifically, this research aims to take advantage of the natural phonaesthetic connections people make between sonic and visual elements. The final output of this research consists of a generative design system that uses auditory data to create visualisations of New Zealand bird song. These visualisations have a mathematical basis, as well as being audio-visual artworks in themselves.</p>

Synaesthetic Sanctuary

<p><b>Traditional scientific methods of visualising sound data have focused on techniques that attempt to capture distinct elements of the audio signal, such as volume and length. However, existing methods such as spectrograms and waveform analysis are limited in their expression of the characteristics associated with complex sounds such as bird song. This research explores strategies to visualise sound in an aesthetically engaging manner. It uses sound data from native New Zealand birds as a design tool for creating an audio-visual design system. The distinct focus on timing and pitch within these songs makes the data suitable for visual comparison. The design techniques explored throughout this research project attempt to express the unique characteristics of a variety of New Zealand bird songs and calls. It investigates how artistic audio-visual methods can be integrated with scientific techniques so that the auditory data can be made more accessible to non-specialists.</b></p> <p>More specifically, this research aims to take advantage of the natural phonaesthetic connections people make between sonic and visual elements. The final output of this research consists of a generative design system that uses auditory data to create visualisations of New Zealand bird song. These visualisations have a mathematical basis, as well as being audio-visual artworks in themselves.</p>

Synaesthetic Sanctuary

<p><b>Traditional scientific methods of visualising sound data have focused on techniques that attempt to capture distinct elements of the audio signal, such as volume and length. However, existing methods such as spectrograms and waveform analysis are limited in their expression of the characteristics associated with complex sounds such as bird song. This research explores strategies to visualise sound in an aesthetically engaging manner. It uses sound data from native New Zealand birds as a design tool for creating an audio-visual design system. The distinct focus on timing and pitch within these songs makes the data suitable for visual comparison. The design techniques explored throughout this research project attempt to express the unique characteristics of a variety of New Zealand bird songs and calls. It investigates how artistic audio-visual methods can be integrated with scientific techniques so that the auditory data can be made more accessible to non-specialists.</b></p> <p>More specifically, this research aims to take advantage of the natural phonaesthetic connections people make between sonic and visual elements. The final output of this research consists of a generative design system that uses auditory data to create visualisations of New Zealand bird song. These visualisations have a mathematical basis, as well as being audio-visual artworks in themselves.</p>