Avian bioacoustics in urbanizing landscapes: relationships between urban noise and avian singing behavior
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Date
2007-06
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The Ohio State University
Abstract
Song is a defining characteristic in avian communication systems because of its
role in mate attraction, territory establishment, territory defense, and habitat selection.
Therefore, biologists are increasingly concerned about potential behavioral and
reproductive consequences of anthropogenic noise as it creates novel acoustic
environments for birds. In this study, I examine the extent to which acoustic noise in
urban environments influences the song characteristics and/or singing behavior of
passerines. I predicted that, in response to loud noises, birds may (1) increase singing
rate and/or repetition of songs (including percent of time spent singing), and (2) adjust
song characteristics such as pitch (frequency) and song length. Both of these strategies
have the potential to improve signal transmission by reducing overlap of signals with
ambient noise. Preliminary decibel level data were collected in four a priori
environments to establish the amount of noise disturbance in relation to the type of urban
area. From May – July 2006, song frequency, duration, and singing rate were measured
for 42 Northern Cardinals (Cardinalis cardinalis) and 53 American Robins (Turdus
migratorius) in forests located within these four increasingly louder acoustic
environments (rural to residential, commercial, and highway) in central Ohio. Song
characteristics were digitally measured via computerized spectrogram analysis. As
predicted, frequency range was positively correlated to noise level for both species.
These data suggest that anthropogenic noise may influence avian singing behavior and
therefore has the potential to be a relatively novel selective force in urban areas.
Description
Will be presented at the 21st International Bioacoustics Congress in Pavia Italy in September of 2007, then pulished in the proceedings from the congress.
Keywords
bioacoustics, Northern Cardinal, American Robin, avian, singing behavior, urbanization