Noise Pollution Filters Bird Communities Based on Vocal Frequency

Abstract

BackgroundHuman-generated noise pollution now permeates natural habitats worldwide, presenting evolutionarily novel acoustic conditions unprecedented to most landscapes. These acoustics not only harm humans, but threaten wildlife, and especially birds, via changes to species densities, foraging behavior, reproductive success, and predator-prey interactions. Explanations for negative effects of noise on birds include disruption of acoustic communication through energetic masking, potentially forcing species that rely upon acoustic communication to abandon otherwise suitable areas. However, this hypothesis has not been adequately tested because confounding stimuli often co-vary with noise and are difficult to separate from noise exposure.Methodology/Principal FindingsUsing a natural experiment that controls for confounding stimuli, we evaluate whether species vocal features or urban-tolerance classifications explain their responses to noise measured through habitat use. Two data sets representing nesting and abundance responses reveal that noise filters bird communities nonrandomly. Signal duration and urban tolerance failed to explain species-specific responses, but birds with low-frequency signals that are more susceptible to masking from noise avoided noisy areas and birds with higher frequency vocalizations remained. Signal frequency was also negatively correlated with body mass, suggesting that larger birds may be more sensitive to noise due to the link between body size and vocal frequency.Conclusions/SignificanceOur findings suggest that acoustic masking by noise may be a strong selective force shaping the ecology of birds worldwide. Larger birds with lower frequency signals may be excluded from noisy areas, whereas smaller species persist via transmission of higher frequency signals. We discuss our findings as they relate to interspecific relationships among body size, vocal amplitude and frequency and suggest that they are immediately relevant to the global problem of increases in noise by providing critical insight as to which species traits influence tolerance of these novel acoustics.

Anthropogenic noise weakens territorial response to intruder's songs

“…Our results suggest that conspecific territorial defense behaviors for both species are impaired with increases in background noise levels and add to the body of evidence supporting noiseinfluenced shifts in bird behavior (Pohl et al 2009, Francis et al 2011a, b, 2012b, Slabbekoorn 2013. Our focus on the effects of acoustic masking from chronic noise at compressor sites in a natural system, as opposed to lab-based, intermittent, or experimentally introduced noise (Lohr et al 2003, Slabbekoorn and Peet 2003, Pohl et al 2009, Halfwerk et al 2011) provides needed field-based evidence that auditory surveillance is impaired by chronic noise.…”

“…Others have produced strong support for a relationship between the frequency of a species' song and habitat use with relation to noise, showing that birds with low-pitched vocalizations may experience more masking by low frequencies and are less common in loud areas relative to less noisy areas (Francis et al 2011a, Goodwin and Shriver 2011, Proppe et al 2013, Francis 2015. These studies show how producing signals that escape noise-masking might be important to successful communication.…”

Learning to cope: vocal adjustment to urban noise is correlated with prior experience in black-capped chickadees

“…Urban noise pollution may affect the diversity, density and breeding success of local avian communities [1][2][3][4]. Detrimental effects may be due to physiological stress and deterrence, but may also be due to acoustic interference when traffic noise overlaps in time and frequency with songs and calls of birds [5 -7].…”

An experimental investigation into the effects of traffic noise on distributions of birds: avoiding the phantom road

“…Francis et al [5] used a similar system of noisy gas compressors and quiet well pads in New Mexico to show that species richness of birds is greatly reduced at noisy sites, with 14 species avoiding areas surrounding gas compressors. Evidence from gas fields indicates that species remaining in noisy areas are those that vocalize within frequencies less masked by anthropogenic noise [6,7]-a phenomenon probably occurring in areas exposed to traffic noise. For example, birds that vocalize at frequencies similar to those of road noise are more likely to avoid roads than species that vocalize at higher frequencies [8,9].…”