Clayton H. Riddell Faculty of Environment, Earth, and Resources

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Browsing Clayton H. Riddell Faculty of Environment, Earth, and Resources by Author "Antze, Bridget"

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    Ability to alter song in two grassland songbirds exposed to simulated anthropogenic noise is not related to pre-existing variability.
    (Taylor and Francis, 2018) Curry, Claire M.; Antze, Bridget; Warrington, Miyako H.; Des Brisay, Paulson G.; Koper, Nicola
    Organisms encounter noise naturally in the environment. However, increasing prevalence of human-caused noise seems to be resulting in behavioural changes in many animals that can affect survival and reproduction. Not all species react the same way to noise; some adjust their vocal signals while others do not. We hypothesized that species with more variability in their vocal signals would be better able to adjust their signals to be audible over anthropogenic noise. We tested this within a large-scale manipulative experiment by recording songs of two grassland songbirds, Baird’s sparrow (Ammodramus bairdii) and Savannah sparrow (Passerculus sandwichensis), both of which are found in areas increasingly affected by energy extraction noise. We compared these species because Savannah sparrows have more variability in their songs geographically and temporally compared to Baird’s sparrows. We recorded both species’ songs before, during, and after high-fidelity playbacks of oil well drilling noise. Surprisingly, both species changed parts of their songs in the presence of noise (Baird’s sparrow usually decreasing frequency and Savannah sparrow increasing frequency) and these changes were not related to seasonal, song, or syllable variability. We suggest instead that acoustically heterogeneous environments may favor the evolution of species that are capable of adjusting their songs in response to variable ambient noise.
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    Savannah sparrows (Passerculus sandwichensis) nesting close to energy infrastructure alarm call at a lower frequency
    (Taylor and Francis, 2018) Antze, Bridget; Koper, Nicola
    Many birds rely on alarm calls during nest defense to communicate about risk, but anthropogenic disturbance, including noisy industrial infrastructure, has the potential to disrupt alarm communication. Birds may overcome these effects by altering the structure of vocalizations to improve signal transmission. While previous work has demonstrated that birds can alter the structure of songs in the presence of noise, few have considered effects of noise-producing infrastructure on alarm call structure. Here, we tested whether Savannah sparrows (Passerculus sandwichensis) altered the structure of alarm calls in the presence of natural gas compressor stations or grid-powered or generator-powered screw pump oil wells, and in relation to overall ambient noise levels. Savannah sparrows called at a lower peak frequency and first quartile frequency close to gas compressor stations, but call structure did not differ with proximity to either type of oil well, or in response to ambient noise levels, suggesting that factors beyond noise amplitude, such as the physical footprint of the infrastructure, affected call structure close to compressor stations. Our results demonstrate that even unlearned, structurally simple avian vocalizations can vary in structure, and that the impacts of anthropogenic infrastructure on acoustic communication may be driven by factors beyond just noise.