Reproductive success of Mexican spotted owls (Strix occidentalis lucida) in relation to common environmental noise ― biotic, non-military aircraft, and weather-related Free

From 2000 to 2005, noise in Mexican spotted owl habitat in the Gila National Forest, NM, was monitored using an array of Larson-Davis (LD) sound level meters (SLMs). Thirty-nine SLMs were deployed across a 20 km x 24 km area, collecting 2-s time interval data mid-April to July, resulting in over 350,000 hr of data. Time-history profiles could be used to attribute many events to sources reliably when SNR exceeded the background by 5-10 dB. The events were categorized as biotic (insects and chorusing birds), thunder, regional commercial jet aircraft, and local air traffic (recreational and firefighting). Measured by the proportion of 2-s samples with L_Aeq > 60 dB, biotic sources and thunder were the most important. Regional commercial jet traffic was the most significant anthropogenic source, accounting for 2% of the total. Based on cumulative sound exposure, thunder was the greatest contributor. Regression techniques were used to relate owl reproductive success to noise metrics by source. Biotic noise was the only significant correlate, highly and positively related to owl reproductive success. The most reasonable interpretation was a strong relationship between biotic noise and owl prey base [Work supported by U.S. Air Force ACC/CEVP.]