This paper describes an experiment conducted in the field to assess the response of seabirds to helicopter overflights. It also attempts to assess the importance of a visual cue to aircraft overflights as compared to the acoustic cue. The work reported here is for a species of sea bird nesting on the Great Barrier Reef in Australia – and it is not so much the results from this particular species that is important in the Canadian context – but more the approach to experimental technique, and the emphasis on good measurement of both disturbance stimulus and disturbance reaction. The finding in this study that visual stimulus appears to be much more important than the acoustic stimulus, if replicable in other species, allows the use of experiments where aircraft overflights are simulated – avoiding some of the ethical dilemmas associated with real life experiments on wild populations.