EFFECTS OF HELICOPTER NOISE ON MEXICAN SPOTTED OWLS

摘要: Military helicopter training over the Lincoln National Forest (LNF) in southcentral New Mexico has been severely limited to protect nesting Mexican spotted owls (Strix occidentalis lucida). To evaluate and nonnesting owl responses noise, we measured flush frequency, distance, alert behavior, response duration, prey delivery rates, female trips from nest, nest attentiveness during manipulated nonmanipulated periods, 1995-96. Chain saws were included our manipulations increase experimental options facilitate comparative results. We analyzed stimulus events by measuring noise levels as unweighted one-third-octave band levels, applying frequency weighting resultant spectra, calculating sound exposure level for total energy (SEL) 0.5-sec equivalent maximum (LEQ max 0.5-sec) helicopters, 10-sec average avg. 10-se) chain saws. An owl-weighting (dBO) curve was estimated emphasize middle range where strigiform have highest hearing sensitivity. Manipulated sites did not differ repro- ductive success (P = 0.59) or number of young fledged 0.12). As distance decreased, increased, regardless type season. recorded no flushes when stimuli >105 m away. Spotted returned predisturbance behavior within 10-15 min after a event. All adult season occurred juveniles had left nest. rates helicopters between (13.3%) seasons (13.6%; P 0.34). SEL <102 dBO (92 dBA) LEQ -59 (46 dBA). more disturbing than flights at comparable distances. Our data indicate 105-m buffer zone overflights on LNF would minimize any potential effects activity.