Temporal changes in songbird vocalizations associated with helicopter noise in Hawai'i's protected natural areas

• Published in: Landscape ecology 2021-03, Vol.36 (3), p.829-843
• Main Authors: Gallardo Cruz, Karen V., Paxton, Kristina L., Hart, Patrick J.
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Biological effects; Biomedical and Life Sciences; Birds; Ecology; Environmental Management; Helicopters; Human influences; Landscape Ecology; Landscape/Regional and Urban Planning; Life Sciences; Nature Conservation; Noise; Passeri; Protected areas; Research Article; Side effects; Songbirds; Species; Sustainable Development; Transportation noise; Vocalization behavior
• ISSN: 0921-2973; 1572-9761
• DOI: 10.1007/s10980-020-01179-2

Context Anthropogenic noise is relatively new to natural soundscapes and may have adverse effects on acoustically active species. In birds, adverse effects include changes in vocalization patterns. Helicopters and songbirds are ubiquitous in protected natural areas but the effect of helicopter noise on songbirds has never been assessed. Objectives Our objective was to determine if helicopter noise affects temporal characteristics of songbird vocalizations within protected natural areas. Methods We collected soundscape recordings in three protected areas with varying levels of helicopter tour activity, including one with the second highest air tour activity in the United States. We examined songbird response to helicopter noise at the species level by measuring changes in vocalization time, and at the community level by employing the Bioacoustic Index, an acoustic measure of biological sound. Results We found a strong association between increasing helicopter noise and songbird vocalizations, indicating that some bird species use temporal shifts in vocalizations to mitigate masking effects from helicopter noise. The strength and direction of the response was species-specific, suggesting differences in resilience to helicopter noise between species. Furthermore, our results suggest that bird response to helicopter noise is strongest in areas with very loud and frequent helicopter traffic. Conclusions Our study is the first to examine and demonstrate impacts of helicopter noise on songbird vocalizations. Our results may serve as the foundation of an air tour management plan that considers reducing the number of helicopter overflights over protected natural areas and enforcing higher flight altitudes to decrease noise power levels.