Predicting the effects of masking noise on communication distance in birds.

Abstract

Anthropogenic noise (e.g., highway noise) that exceeds natural ambient sound levels potentially can mask important acoustic signals used by birds during communication. Signals degraded by masking can in turn adversely affect critical behaviors such as mate attraction, territorial defense, parent-offspring communication, predator avoidance, and prey detection. The amount of masking depends not only on the physical characteristics of the noise (intensity, frequency, temporal pattern, etc.) but also the auditory capacity of the species, the acoustic structure of their vocal signals, the proximity of the birds to the noise source and each other, and the sound attenuation properties of the habitat. Here we present a quantitative model for predicting effective communication distances between birds subject to different levels and types of anthropogenic noise. Cross-species analysis shows that communication distances are largely context/environment dependent and species specific. Extrapolation of noise impact distance estimates even within groups of similar species should be exercised with caution. This model should be useful in environmental impact analysis of anthropogenic noise on birds and other wildlife, particularly species of conservation concern.