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The California spotted owl (Strix occidentalis occidentalis) is an older‐forest associated species that resides at the center of forest management planning in the Sierra Nevada and Southern California, USA, which are experiencing increasingly large and severe wildfires and drought‐related tree mortality. We leveraged advances in passive acoustic survey technologies to develop an acoustically assisted survey design that could increase the efficiency and effectiveness of project‐level surveys for spotted owls, allowing surveys to be completed in a single year instead of in multiple years. We deployed an array of autonomous recording units (ARUs) across a landscape and identified spotted owl vocalizations in the resulting audio using BirdNET. We then evaluated spatio‐temporal patterns in spotted owl vocalizations near occupied territories and the ability of a crew naïve to the location of occupied territories to locate spotted owls based on patterns of acoustic detections. After only 3 weeks of acoustic surveys, ≥1 ARU within 750 m of all 17 occupied territories obtained spotted owl detections across ≥2 nights. When active surveys using broadcast calling were conducted near ARUs with spotted owl detections by surveyors naïve to territory occupancy status and locations, surveyors located owls in 93% to 100% of occupied territories with ≤3 surveys. To further improve the efficiency of spotted owl surveys, we developed a statistical model to identify and prioritize areas across the Sierra Nevada for different survey methods (active only, acoustically assisted, no surveys) based on the expected probability of occupancy predicted from remotely sensed measurements of tree height and historical occupancy. Depending on managers' tolerance for false negatives, this model could help identify large areas that might not benefit from surveys based on low expected occupancy probabilities and areas where acoustically assisted surveys might enhance survey effectiveness and efficiency. Collectively, these findings can help managers streamline the survey process and thus increase the pace of forest restoration while minimizing potential near‐term adverse effects on California spotted owls. [ABSTRACT FROM AUTHOR]

Vocal territory defense can vary within a species due to many factors such as sex and breeding status, influencing territory size and thus population density across a landscape. Therefore, understanding what influences variation in territorial vocalizations can help to illuminate trade‐offs between territoriality and other life history demands, which benefits our general understanding of animal ecology as well as helps to inform emerging passive acoustic monitoring approaches. Here, we investigated how sex and breeding status affected territoriality and vocal behavior in the California spotted owl Strix occidentalis occidentalis in the Sierra Nevada, California, USA, using high‐resolution acoustic/GPS tags. We discovered that territorial vocal behavior was related to breeding status and to a lesser extent sex. Breeding owls with fledged young had a less diverse vocal repertoire, produced fewer and quieter territorial calls, and typically called only when close to their nest. Males were also more likely to engage in territorial calling than females. Breeding spotted owls also maintained significantly smaller territories – but utilized larger home ranges – than non‐breeding individuals. Our results suggest that breeding spotted owls may reduce their investment in territorial behaviors to mitigate the demands and risks associated with rearing young. Further, our results have important implications for the passive acoustic monitoring of spotted owls and, more broadly, highlight the utility of using multiple call types to detect species of interest. [ABSTRACT FROM AUTHOR]

Passive acoustic monitoring adds to knowledge of whale presence and distribution over space and time. The gray whale (Eschrictius robustus) undertakes an annual migration between remote feeding and breeding locales, with its highly sonorous nature suggesting employment of low-frequency calls to be inherent to travel behaviours, perhaps aiding navigation and social cohesion. We consider whether these calling behaviours can be used to better understand the process of migration, where call presence and relative abundance might represent a means to track the progress of migrating whales. Passive acoustic recordings made on the west coast of Vancouver Island, a mid-way point of gray whale migration, were first analysed for abundance over time to examine the progression of migration. Then the acoustic record was compared to shore-based recordings undertaken from Point Vincente, California to better assess their use as a census tool. The timing in peaks of calling, particularly of far-ranging moan-like calls, and shore counts showed a high degree of congruence when considered with a lag time of 8 days to account for travel time between the two survey locations. This suggests that passive acoustic monitoring could complement the long running and shore-based counts in recording annual population movement, and add to our understanding of gray whales on poorly known segments of their migration route or at times when visual observations are not possible. Image 1 • Passive acoustics compared to visual counts to assess use as migration census tool. • Congruence between acoustic and visual data comparing peaks. • Case study of gray whale migration, highly sonic whales during travel. • Can use moan calls to track migration progress. • Can inform more of the migration process and route. [ABSTRACT FROM AUTHOR]