Adaptación acústica del canto de Turdus leucomelas (Passeriformes: Turdidae) a diferentes niveles de ruido antrópico, en el área metropolitana de Belém de Pará, Brasil

Abstract

Adaptación acústica del canto deAbstract: Acoustic adaptation in Turdus leucomelas (Passeriformes: Turdidae) songs to different levels of anthropogenic noise, in the metropolitan area of Belem, Para, Brazil. Anthropogenic noise in urban environments is a major challenge for those species that depend on the transmission of acoustic signals to communicate. To avoid being masked by background noise, some bird species are able to make adjustments in their songs. Studies on vocal adjustment for tropical birds are still scarce and are of interest since both the urban structure and the vegetation associated with urban habitats differ significantly with respect to the cities of temperate climates.In this research we studied the changes in the song parameters of the pale-breasted thrush (Turdus leucomelas) in an urban environment of the metropolitan area of Belém (Brazil). To this end, bird songs were recorded and ambient noise was measured between September and November 2008, in three different acoustic environments (urban, suburban and rural) along an urban gradient. The songs of 12 individuals per area were selected (a total of 36). Possible differences between song parameters were analyzed by ANOVAs. To assess the noise impact on bird song, we only considered the spectrum of environmental noise within the range of vocalizations of the species. In general, birds of urban habitats presented songs with higher maximum frequencies and with a wider range of notes, than their counterparts in suburban and rural areas. The differences were more pronounced in relation to rural areas. No differences in the minimum frequencies, the concentration of energy, or the average duration of the notes were found. These results differ from other studies and could possibly indicate variations in the way birds try to succeed in habitats with high ambient noise. It is necessary further exploration on the role of these changes in the effective improvement of intra-specific communication for the species in such environments. Rev. Biol. Trop. 65 (2): 633-642. Epub 2017 June 01.

Exposure to noise pollution across North American passerines supports the noise filter hypothesis

“…Work on the noise filter hypothesis has focused on either the minimum or the peak frequencies of vocalizations. Although the minimum frequency of vocalizations are most masked by anthropogenic noise and, within species, most often found to change in urban or noisy environments (e.g., Hu & Cardoso, 2010; Job et al, 2016; Redondo et al, 2013; Slabbekoorn & Boer‐Visser, 2006; Walters et al, 2019; Wood & Yezerinac, 2006; but see also Mendes, Colino‐Rabanal, & Peris, 2017), species differences in minimum frequency do not appear to be the best acoustic predictor of noise tolerance. For example, bird species occurring in cities were found to have, on average, higher peak frequencies but not higher minimum frequencies than closely related species not described as regularly inhabiting urban habitats (Hu & Cardoso, 2009).…”

Variación del canto de Myiothlypis fulvicauda (Parulidae) en ambientes naturales de Ibagué (Tolima, Colombia)

“…Lo anterior podría contribuir a que el canto (o parte de este) se transmita a pesar del ruido ambiental, especialmente en temporada lluviosa, cuando el ruido es mayor (Kirschel et al, 2009). Resultados similares han sido reportados para las especies Pitangus sulphuratus y Turdus leucomelas (Mendes et al, 2017;Mendoza & Arce-Plata, 2012).…”

Urban cycles of human activity do not significantly alter the behaviour of a duetting bird

“…Singing effort and song length did not vary significantly relative to the weekly cycles in human activity, suggesting that birds did not increase signal redundancy as human activity levels increased. Unexpectedly, birds emitted duets with slightly higher maximum frequency (~80 Hz) on weekends than on weekdays (Mendes et al 2011(Mendes et al , 2017, whereas minimum frequency was unrelated to weekly cycles of human activity levels. We suggest that changes in the physical obstacles or barriers to sound propagation, and not noise, are more probable explanations for the slightly lower pitched Rufous Hornero duets on weekdays.…”