Evolution of the dawn chorus throughout the breeding season at an inland migratory bird refuge

Abstract

The dawn chorus is a defining acoustic event for many environments with vocal bird populations. To study short and long-term changes in spectral characteristics of the dawn chorus at an inland migratory bird refuge, Larson Davis 831C sound level meters (SLM) were deployed at Utah’s Bear River Migratory Bird Refuge from March to August in 2021 and 2022, overlapping with the breeding seasons of many resident and migratory species of birds. The SLMs collected one-second temporal resolution data in one third octave (OTO) frequency resolution both years, as well as audio recordings during 2022. The relative contributions of the bird-relevant OTO bands (∼500 Hz–12.5 kHz) to the total energy are analyzed for each chorus. One result shows that the chorus’s spectral composition varies markedly for different locations within the refuge throughout the breeding season. The results show the value of the relatively low-resolution data in studying overall chorus characteristics. Additionally, the audio recordings have been analyzed using BirdNET species identification software to correlate changes in chorus characteristics with changes in species and behavior over the breeding season.