Do the Calls of a Bird, the Noisy Miner (Manorina melanocephala), Need Adjustment for Efficient Communication in Urban Anthropogenic Noise?

A common feature of urban environments is constant, low frequency, anthropogenic noise. To communicate effectively acoustically in this environment requires avoidance of sound masking by this background noise. Research suggests that some animals can adjust their vocalizations so that they lie outside the main frequency range of urban anthropogenic noise, whilst others may produce sound signals that naturally avoid masking and therefore do not require adjustment. To date, research in this area has tended to focus on adjustment to complex songs, rather than simpler calls. The Noisy miner, Manorina melanocephala, is a very successful avian urban colonizer that uses calls in its acoustic communication. We compared the calls of this species in both urban and rural populations. Of all calls compared, only those that lay within the main frequency range of anthropogenic noise (1–2 kHz) showed shifts in minimum sound frequency in urban individuals, but these frequency shifts were notably small and insufficient to entirely preclude masking by urban noise. However, several Noisy miner calls had frequencies of more than 2 kHz that lay outside the main frequency range of urban anthropogenic noise (>2 kHz), suggesting intriguingly that this species may be inherently well-suited to communicating vocally in urban settings, which may be one of the keys to its success as an urban colonizer