UC Santa Cruz

Passive acoustic monitoring is a transformative tool for increasing the scale of ecological monitoring. The biggest challenges remain in analyzing large volumes of recordings to produce ecological information useful for decision making. Ecoacoustics, a holistic, quantitative analysis of soundscapes and their emergent properties is an appealing way to distill information from many recordings, but new tools require rigorous studies to measure their efficacy tracking ecological patterns. This thesis contains three studies testing the efficacy of ecoacoustic approaches to monitoring species and communities. The first study uses simulations to test if a variety of indices of soundscape complexity, intensity and differences can measure realistic bird community changes in simulated dawn choruses. In addition, I explore combining indices to increase predictive power, and how the addition of anthropogenic noise and changes in bird behavior impact the usefulness of acoustic indices. The second study examines the acoustic monitoring of Cassin’s Auklets (Ptychoramphus aleuticus), a chorusing colonial seabird that is notoriously challenging to monitor. I test how a traditional automated call detection compares to a novel approach based on energy spectrums of the entire soundscape to index auklet activity. I discuss how for some species, this approach may be more effective in indexing activity, and in this case is a reliable predictor or relative burrow density, and could be applicable for other nocturnal, vociferous seabirds. In the third study I move from single seabird species to seabird communities. I apply acoustic indices of soundscape differences, complexity and intensity to measure seabird restoration outcomes in the Western Aleutian Islands. I find that acoustic richness, and the spectral differences from a pristine reference island are predicted by years of seabird recovery and other factors that promote seabird recovery. Acoustic indices provided similar information to traditional and more laborious approaches. In summation, ecoacoustic approaches are a valuable part of the acoustic monitoring toolbox. Across all three studies, acoustic indices reflected meaningful ecological patterns, at a fraction of the time and effort needed for other approaches. This can greatly improve the scale and speed at which monitoring programs can inform management decisions and iteratively improve conservation outcomes.