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Dr. Darren S Proppe
Calvin College, Grand Rapids, MI
Objective
To investigate how varying levels and types of ambient noise affect the detectability of bird vocalizations using passive acoustic monitoring and Kaleidoscope detection software.
Methods
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Field Sites: 20 remote hardwood forest locations; 16 complete trials.
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Setup: Two SM4 recorders per site, with one exposed to controlled playback of white, pink, or brownian noise at 40–70 dB(A), and one as a control.
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Target Species: Blue jay, ovenbird, red-eyed vireo, Eastern wood-pewee, and black-throated green warbler.
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Analysis Tools: Kaleidoscope Pro for automated detection; R (v3.3.3) for statistical modeling; human observation for comparison.
Key Findings
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Noise ≥ 50 dB significantly reduced vocalization detections; at ≥70 dB, detections were nearly eliminated.
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Pink and brownian noise caused more masking than white noise, likely due to overlap with bird vocal frequencies.
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Detection rates varied by species, but all were affected by noise to some extent.
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Human vs. automated detection comparisons are underway to evaluate software limitations under noisy conditions.
Implications
These findings highlight the importance of accounting for ambient noise in bioacoustic monitoring, especially in human-altered landscapes. Passive acoustic surveys may underestimate bird presence in noisy environments, leading to biased ecological conclusions.
Figure 1: Mean of correct detections from noise and control treatments recorded over the same timeframe. Error bars represent standard error.
Figure 2: Predictions from the fitted model of correct detections for three different noise frequencies (brownian, pink, and white) with increasing amplitude of noise playback.
Figure 3: Predictions from the fitted model of correct detections for five different bird species with increasing amplitude of noise playback. Species inlclude' A) blue jay (BLJA), black-throated green warbler (BTNW), ovenbird (OVEN), Eastern wood-pewee (EAWP), and B) red-eyed vireo (REVI)
References
Kight, C. R., Saha, M. S., & Swaddle, J. P. (2012). Anthropogenic noise is associated with reductions in the productivity of breeding Eastern Bluebirds (Sialia sialis). Ecological Applications, 22(7), 1989-1996.
Koper, N., Leston, L., Baker, T. M., Curry, C., & Rosa, P. (2016). Effects of ambient noise on detectability and localization of avian songs and tones by observers in grasslands. Ecology and evolution, 6(1), 245-255.
Leonard, M. L., Horn, A. G., Oswald, K. N., & McIntyre, E. (2015). Effect of ambient noise on parent-offspring interactions in tree swallows. Animal behaviour, 109, 1-7.
Francis, C. D., Ortega, C. P., & Cruz, A. (2011). Vocal frequency change reflects different responses to anthropogenic noise in two suboscine tyrant flycatchers. Proceedings of the Royal Society B, 278(1714), 2025-2031.
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