Song adjustments only partially restore effective communication among Baird's sparrows, Centronyx bairdii, exposed to oil well drilling noise

Noise from oil and gas development is pervasive across many landscapes and creates a novel soundscape that wildlife must adapt to or avoid. In response to anthropogenic noise, many wildlife species alter their vocalizations. Some adjusted vocalizations may promote effective communication in the presence of noise by improving detection and preserving information about the sender's status. However, if adjusted vocalizations fail to improve communication in noise, both missed detections and misinterpretations of vocalizations could impact the fitness of individuals and ultimately contribute to population declines. Baird's sparrow is a species at risk in Canada that adjusts its songs in response to oil well drilling noise by altering whole-song elements such as decreasing the peak frequency of songs (Curry et al., 2017, Bioacoustics, 27(2), 105-130). We examined the efficacy of these adjusted songs in the mixed-grass prairies of southern Alberta, Canada during the Baird's sparrow breeding season (May-July 2018 and 2019) using a repeated measures study design (N = 69 dyads) in which we simulated territorial intrusions by broadcasting adjusted songs and unadjusted songs in the presence and absence of oil well drilling noise recordings. We found that focal male behaviour was mainly mediated by noise treatment when compared to song treatment. In noisy trials, males sang less, called more and performed more flybys, regardless of song treatment type. However, in noisy trials, males displayed longer song latency in response to unadjusted songs compared to adjusted songs. The results of our novel study suggest that the presence of oil well drilling noise elicits more aggressive territorial defence behaviour in Baird's sparrows or hinders the ability of individuals to locate or assess rivals. Additionally, our results suggest that adjusted songs only partially restore effective communication in noise. Crown Copyright (c) 2024 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).