Tuesday, February 08, 2011

More Evidence that Birds Can Adapt to Urban Noise Conditions

A new study by researchers from Universidad Nacional Autónoma de México and the Museo Nacional de Ciencias Naturales shows that House Finches are capable of making short-term adjustments to their vocalizations in urban environments, which typically are louder than more natural environments.

The study suggests that some bird species are capable of adapting to urban acoustic environments.


Experimental evidence for real-time song frequency shift in response to urban noise in a passerine bird

Eira Bermúdez-Cuamatzin, Alejandro A. Ríos-Chelén,Diego Gil and Constantino Macías Garcia

doi: 10.1098/rsbl.2010.0437
Biol. Lett. 23 February 2011 vol. 7 no. 1 36-38

Research has shown that bird songs are modified in different ways to deal with urban noise and promote signal transmission through noisy environments. Urban noise is composed of low frequencies, thus the observation that songs have a higher minimum frequency in noisy places suggests this is a way of avoiding noise masking. Most studies are correlative and there is as yet little experimental evidence that this is a short-term mechanism owing to individual plasticity. Here we experimentally test if house finches (Carpodacus mexicanus) can modulate the minimum frequency of their songs in response to different noise levels. We exposed singing males to three continuous treatments: low–high–low noise levels. We found a significant increase in minimum frequency from low to high and a decrement from high to low treatments. We also found that this was mostly achieved by modifying the frequency of the same low-frequency syllable types used in the different treatments. When different low-frequency syllables were used, those sung during the noisy condition were longer than the ones sang during the quiet condition. We conclude that house finches modify their songs in several ways in response to urban noise, thus providing evidence of a short-term acoustic adaptation.