Responses of Mexican spotted owls to low-flying military jet aircraft

Abstract

To investigate the effects of military fixed-wing aircraft training on the behavior of the endangered Mexican spotted owl (Strix occidentalis lucida), we subjected four adults and one juvenile owl to low-altitude, fixed-wing, jet aircraft overflight trials in Colorado in 1996 and 1997. Trials consisted of three sequential fly-bys, each at a greater aircraft speed and noise level, over owl territories in narrow and steep-walled canyons. All overflights were about 460 m above canyon rims, the lowest altitude allowed during training flights. Maximum noise levels, measured at one owl site, were 78, 92, and 95 dB (sound volume) for the first, second, and third fly-bys, respectively. Behaviors of owls during 25-second fly-by periods ranged from "no response" (no body movements) to "intermediate response" (sudden turning of head). The 25-second fly-by responses did not exceed behaviors ("no movement" to "change of roost") exhibited by the owls during 10-minute pre- and postflight observation periods before and after each fly-by.

Citation

Johnson, Charles L.; Reynolds, Richard T. 2002. Responses of Mexican spotted owls to low-flying military jet aircraft. Res. Note RMRS-RN-12. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 4 p.