Effects of ambient noise on detectability and localization ofavian songs and tones by observers in grasslands.

Nicola Koper,Tyne M Baker,Lionel Leston,Claire Curry,Patricia Rosa

doi:10.1002/ece3.1847

Nicola Koper, Tyne M Baker + Show 3 more

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https://doi.org/10.1002/ece3.1847

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Abstract

Probability of detection and accuracy of distance estimates in aural avian surveys may be affected by the presence of anthropogenic noise, and this may lead to inaccurate evaluations of the effects of noisy infrastructure on wildlife. We used arrays of speakers broadcasting recordings of grassland bird songs and pure tones to assess the probability of detection, and localization accuracy, by observers at sites with and without noisy oil and gas infrastructure in south-central Alberta from 2012 to 2014. Probability of detection varied with species and with speaker distance from transect line, but there were few effects of noisy infrastructure. Accuracy of distance estimates for songs and tones decreased as distance to observer increased, and distance estimation error was higher for tones at sites with infrastructure noise. Our results suggest that quiet to moderately loud anthropogenic noise may not mask detection of bird songs; however, errors in distance estimates during aural surveys may lead to inaccurate estimates of avian densities calculated using distance sampling. We recommend caution when applying distance sampling if most birds are unseen, and where ambient noise varies among treatments.

Highlights

It has long been recognized that detectability of birds during field surveys is imperfect (e.g., Anderson 2001; Johnson 2008; Efford and Dawson 2009)
Distance from infrastructure, ambient noise level, and interactions were insignificant in all models, indicating that ambient noise had no effect on detectability (Table 1)
We did not find strong effects of noise on detectability or localization accuracy. These results differed from other studies that have evaluated effects of compressor station noise on detectability (Blickley and Patricelli 2010; Ortega and Francis 2012), but are somewhat consistent with the observations of Pacifici et al (2008), who found that detections within 50 m of observers were independent of ambient noise levels

Summary

Introduction

It has long been recognized that detectability of birds during field surveys is imperfect (e.g., Anderson 2001; Johnson 2008; Efford and Dawson 2009). Statistical methods that adjust for detection probability may create biases greater than those of unaltered indices (Efford and Dawson 2009); the effect and risk of these biases varies among habitat types (Johnson 2008). It is, important to evaluate detectability of birds under a variety of conditions that are likely to be encountered during field surveys, to understand potential biases and so that costs and benefits of adjusting for imperfect detectability can be assessed

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