Predators are among the most threatened animal groups globally, with prey declines contributing to their endangerment. However, assessments of the habitat conditions that influence the successful capture of different prey species are rare, especially for small, cryptic predators. Accordingly, most predator conservation plans are based on the relative importance of habitats inferred from coarse-scale studies that do not consider habitat features contributing to hunting success, which can vary among prey species. To address this limitation, we integrated high-resolution GPS tracking and nest video monitoring to characterize habitat features at prey capture locations during the nestling provisioning stage for the Spotted Owl (Strix occidentalis) a small, cryptic predator that has been at the center of a decades-long forest management conflict in western North America. When all prey species were considered collectively, males provisioning nests tended to capture prey: (1) in areas with more large-tree forest, (2) in areas with more medium trees/medium canopy forest, and (3) at edges between conifer and hardwood forests. However, when we considered the owl’s two key prey species separately, males captured woodrats (Neotoma fuscipes) and Humboldt flying squirrels (Glaucomys oregonensis) in areas with markedly different habitat features. Our study provides clarity for forest management in mixed-ownership because different prey species achieve high densities in different habitat types. Specifically, our results suggest that promoting large trees, increasing forest heterogeneity, and creating canopy gaps in forests with medium trees/high canopy cover could benefit Spotted Owls and their prey, which has the ancillary benefit of enhancing forest resilience. Combining high-resolution GPS tagging with video-based information on prey deliveries to breeding sites can strengthen conservation planning for small predators by more rigorously defining those habitat features that are associated with successful prey acquisition.

Owls play important cultural, ecological, and indicator roles throughout the world. Yet owls’ cryptic behavior has led to uncertainties about their basic ecology, including foraging, communication, and functional roles within the community, and potentially hindered the implementation of effective conservation measures. Here we demonstrate the potential for next‐generation GPS tags capable of recording high‐precision, minute‐by‐minute locations paired with other technologies to resolve some of these uncertainties. We combined high‐precision GPS tagging data with infrared (IR) video recorded by arboreally‐mounted cameras at 5 spotted owl (Strix occidentalis) nest sites in the Sierra Nevada, USA to provide a uniquely detailed examination of owl foraging patterns. Our approach allowed us to identify the precise time and location of 54 predation events and prey identity. We also used high‐precision GPS tags with on‐board audio recorders to map the vocal activity of 8 individuals by matching the time of vocalizations in the audio data to GPS locations recorded at one‐minute intervals. The combined spatial and acoustic data revealed that nonbreeding males had the most widespread territorial vocal activity (i.e., producing 4‐note territorial calls), while females provisioning fledglings displayed extensive nonterritorial vocal activity (i.e., producing many contact calls). Thus, the GPS‐tag technologies we employed can provide opportunities to better understand owl foraging, communication, territoriality, and population dynamics. The methods we describe are time‐ and resource‐intensive but can be paired with techniques that are more applicable at landscape scales, such as stable isotope analyses, LiDAR‐based habitat analyses, and passive acoustic monitoring to link local processes to broad‐scale ecological patterns. Therefore, our approach could be applied to many species whose behavior inhibits direct observation. © 2021 The Wildlife Society.

ContextThe concepts of habitat fragmentation and heterogeneity are central to the conservation of biodiversity; yet understanding when landscapes transition from heterogenous to fragmented can challenge conservation in practice. Complex and sometimes difficult-to-measure responses of species, and ultimately biological communities, to habitat heterogeneity and fragmentation may reflect the outcome of life-history trade-offs shaped by different landscape properties. ObjectivesHere, we tested the hypothesis that a mosaic of forest stands improved hunting and breeding success for California spotted owls (Strix occidentailis occidentalis). MethodsWe integrated high-temporal-resolution GPS tags, video monitoring of nests sites, long-term assessments of reproductive status, and high-resolution remotely-sensed vegetation data in a mixed-ownership landscape in the Sierra Nevada, California. ResultsSpotted owls made shorter nocturnal movements when medium forest was prevalent in their territory. However, spotted owls delivered prey at a higher rate to nests sites when they had more forest edge in their territory, which presumably provided greater access to large-bodied woodrat prey. Further, spotted owl reproductive output was relatively high in territories that contained a mix of mature and open forest. ConclusionsThus, the benefits heterogenous forests provide to hunting success appear to outweigh costs associated with additional commuting to foraging sites and provide emergent fitness benefits to spotted owls. We suggest that the line between habitat heterogeneity and fragmentation can be a complex one that varies not only among, but within, species. Further, understanding the effects of heterogeneity and fragmentation on biological communities will require more empirical and mechanistic studies of individual species.

Barred Owls (Strix varia) have recently expanded westward from eastern North America, contributing to substantial declines in Northern Spotted Owls (Strix occidentalis caurina). Passive acoustic monitoring (PAM) represents a potentially powerful approach for tracking range expansions like the Barred Owl’s, but further methods development is needed to ensure that PAM-informed occupancy models meaningfully reflect population processes. Focusing on the leading edge of the Barred Owl range expansion in coastal California, we used a combination of PAM data, GPS-tagging, and active surveys to (1) estimate breeding home range size, (2) identify patterns of vocal activity that reflect resident occupancy, and (3) estimate resident occupancy rates. Mean breeding season home range size (452 ha) was reasonably consistent with the size of cells (400 ha) sampled with autonomous recording units (ARUs). Nevertheless, false positive acoustic detections of Barred Owls frequently occurred within cells not containing an activity center such that site occupancy estimates derived using all detected vocalizations (0.61) were unlikely to be representative of resident occupancy. However, the proportion of survey nights with confirmed vocalizations (VN) and the number of ARUs within a sampling cell with confirmed vocalizations (VU) were indicative of Barred Owl residency. Moreover, the false positive error rate could be reduced for occupancy analyses by establishing thresholds of VN and VU to define detections, although doing so increased false negative error rates in some cases. Using different thresholds of VN and VU, we estimated resident occupancy to be 0.29–0.44, which indicates that Barred Owls have become established in the region but also that timely lethal removals could still help prevent the extirpation of Northern Spotted Owls. Our findings provide a scalable framework for monitoring Barred Owl populations throughout their expanded range and, more broadly, a basis for converting site occupancy to resident occupancy in PAM programs.

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