Abstract:
Mexican spotted owls (Strix occidentalis lucida) were exposed to two types of noisy stimuli: very low altitude helicopter overflights and chain saw activity. The stimuli were presented to the owls at several distances and noise levels during daylight hours in July through September 1995. Responses were characterized into two categories, ``alert'' and ``flight.'' ``Alert'' responses to low altitude helicopter overflights were typical, but ``flight'' responses occurred for only a small percentage of the trials. Chain saw presentations at similar distances elicited ``flight'' responses much more frequently. Consideration was given during data analysis to the owls' hearing range and sensitivity. [Research supported by U.S. Air Force.]