Anthropogenic noise decreases urban songbird diversity and may contribute to homogenization

Abstract

More humans reside in urban areas than at any other time in history. Protected urban green spaces and transportation greenbelts support many species, but diversity in these areas is generally lower than in undeveloped landscapes. Habitat degradation and fragmentation contribute to lowered diversity and urban homogenization, but less is known about the role of anthropogenic noise. Songbirds are especially vulnerable to anthropogenic noise because they rely on acoustic signals for communication. Recent studies suggest that anthropogenic noise reduces the density and reproductive success of some bird species, but that species which vocalize at frequencies above those of anthropogenic noise are more likely to inhabit noisy areas. We hypothesize that anthropogenic noise is contributing to declines in urban diversity by reducing the abundance of select species in noisy areas, and that species with low-frequency songs are those most likely to be affected. To examine this relationship, we calculated the noise-associated change in overall species richness and in abundance for seven common songbird species. After accounting for variance due to vegetative differences, species richness and the abundance of three of seven species were reduced in noisier locations. Acoustic analysis revealed that minimum song frequency was highly predictive of a species' response to noise, with lower minimum song frequencies incurring greater noise-associated reduction in abundance. These results suggest that anthropogenic noise affects some species independently of vegetative conditions, exacerbating the exclusion of some songbird species in otherwise suitable habitat. Minimum song frequency may provide a useful metric to predict how particular species will be affected by noise. In sum, mitigation of noise may enhance habitat suitability for many songbird species, especially for species with songs that include low-frequency elements.

Habitat type, food resources, noise and light pollution explain the species composition, abundance and stability of a winter bird assemblage in an urban environment

“…The effect of noise has so far been studied only with respect to the breeding period (Nemeth et al 2013;Proppe et al 2013): excessive levels of noise have been shown to lead to the homogenization of bird communities. Species with low-frequency calls may be drowned out by the noise of passing motor vehicles, which forces them to call more often, and that, in turn, entails a greater expenditure of energy (Francis et al 2009;Nemeth et al 2013).…”

“…Species with low-frequency calls may be drowned out by the noise of passing motor vehicles, which forces them to call more often, and that, in turn, entails a greater expenditure of energy (Francis et al 2009;Nemeth et al 2013). The upshot is that the least flexible species withdraw from very noisy environments (Proppe et al 2013). In our opinion vocal communication is as important in winter as during the breeding season: species with a similar diet congregate in flocks, searching together for sources of food, and while foraging avail themselves of the common calls warning against predators.…”

Anthropogenic noise weakens territorial response to intruder's songs

“…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.…”

Some lessons from the effects of highway noise on birds

“…The same species sing at higher pitches with elevated man-made noise but not with decreasing canopy cover, suggesting noise is the main factor, that leads to increased song pitch and not vegetation (Proppe et al, 2012). Also, another general notion emerging from some studies is that noise contributes to declines in urban diversity by reducing the abundance of select species in noisy areas, especially species with low frequency songs (Proppe et al, 2013).…”