Measuring the effect of aircraft noise on sea birds

Abstract

This paper reports on a procedure which exposes sea birds to acoustic stimuli simulating aircraft overflights, and is one of the first experiments to attempt to quantify the responses of birds in the wild to noise. The experiment, conducted on Australia's Great Barrier Reef, involved presentation of pre-recorded aircraft noise, with peak overflight levels of 65 dB9A) to 95 dB(A), to nesting sea bird colonies. Sea bird responses were videotaped and these tapes were subsequently analysed by scoring the behavioural response of each bird in the colony. Results of a trial of this experimental procedure for one species, the Crested Tern ( Sterna bergii), indicate that the maximum responses observed, preparing to fly or flying off, were restricted to exposures greater than 85 dB(A). A scanning behaviour involving head-turning was the minimum response, and this, or a more intense response, was observed in nearly all birds at all levels of exposure. However an intermediate response, an alert behaviour, demonstrated a strong positive relationship with increasing exposure. While the experiment has provided good control on simulated aircraft noise levels, preliminary observations of response of the colonies to balloon overflights suggests that visual stimulus is likely to be an important component of aircraft noise disturbance.