The impact of standing water on acoustic characteristics of the dawn chorus in a western bird refuge

Migratory bird refuge soundscapes are seasonally dynamic due to changes in wildlife populations. Some of the most prominent acoustical events in a bird refuge are the morning and evening avian choruses, particularly during spring and early summer when breeding activity of birds is high. This event is acoustically dynamic, reacting to both biotic and abiotic drivers. One such driver is the presence of standing water. For this study, near-continuous spectral data were collected at the U.S. Federal Fish and Wildlife Services Bear River Migratory Bird Refuge. Although data fidelity can be compromised by wind and rain, changes in the avian chorus characteristics over time are observed. These changes over time are observed to correlate with times management at the refuge drained the wetland area surrounding the recording sites. Recording sites that were close to drained wetland units saw decreases in the average sound pressure level during the dawn chorus, sometimes on the order of 20 dB.