Text Box: Environment & We 
An International Journal of Science & Technology
 ISSN: 0975-7112 (Print) 				ISSN: 0975-7120 (Online)
Text Box: Ambient noise levels due to dawn chorus at different habitats in Delhi  

Manoj Singh1, Dinesh Kumar1, Puneeta Pandey2, Krishan Kumar1* and Vinod Kumar Jain1
1School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
2School of Environmnet & Earth Sciences, Central University of Punjab, Bathinda, Punjab, India
*Email: krishan_kumar@mail.jnu.ac.in
The characteristics that enable animals to live in urban environments are not well understood. A high level of ambient noise is a typical signature of an urban habitat, which makes vocal communication difficult for birds. The present study compares the noise levels due to dawn chorus of birds in semi-urban and forest habitats of Delhi region. The noise level measurements were carried out using Type I Sound Level Meter. Time series plots of noise levels at different 1/3rd octave frequency indicates a significant increase in the noise levels in the frequency range of 1-4 kHz during the time of chorus as compared to background noise levels of the site. It is also observed that the dawn chorus of the birds at different sites in Delhi is mainly dominated by two generalist species, i.e., Corvus splendens (House Crow) and Acridotheres tristis (Common Myna). Spectrogram of typical calls by these two species also indicates the dominance of 1-2 kHz in their calls. Whereas the maximum noise levels during the dawn chorus reached up to 70dB levels and even more. Our results show that bird communities vary greatly along the different studied habitats. It is further observed that the urban sites are mainly dominated by a very few species like common myna, house crow, rock blue pigeon, while the species diversity at ridge forest sites is found to be higher, and also includes bulbul, sunbirds and warblers etc. One of the reasons for significantly less number of species contributing to the dawn chorus could be harsh acoustic environments prevailing in the urban areas making the communication among the birds difficult. The results of this study would provide evidence for site dependent behavioral mechanism explaining noise dependent frequency use in bird chorus.
Keywords: Bird chorus, ambient noise, vocalization frequency, house crow, common myna

Environ. We Int. J. Sci. Tech. 6 (2011) 123-134                Full Paper

Volume 6, Number 3

July-September 2011