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opencc-zeroNov 2021View details →

Feather corticosterone reveals developmental challenges in a long‐term study of juvenile northern spotted owls

1. Corticosterone is a steroid hormone integral to a variety of physiological pathways and is strongly associated with the vertebrate stress–response. In avian species, circulating corticosterone is sequestered into developing feathers and is used as an indicator of energy allocation during feather growth and widely applied in conservation physiology. 2. The northern spotted owl (Strix occidentalis caurina) is a federally threatened old–growth forest obligate of conservation concern endemic to the Pacific Northwest of the United States and Canada. The effects of landscape characteristics and individual variation on early development in spotted owls remain unstudied despite long recognition of this knowledge gap and its potential importance to species conservation. 3. We quantified corticosterone concentrations in 4,720 feathers from 1,056 juvenile spotted owls across seven study areas between 2001 and 2017. We used an information–theoretic approach to examine the environmental and individual factors related to feather corticosterone in juvenile spotted owls as an indicator of challenges during early development. 4. Feather corticosterone was positively related to temperature and precipitation, and negatively related to juvenile mass at banding. We found strong support for an interaction between mass and precipitation, with greater amounts of precipitation being associated with higher levels of feather corticosterone in lighter juveniles. The temperature and precipitation metric with the strongest relationship with feather corticosterone occurred during the fledging period, suggesting that this period presents an energetic challenge for juvenile spotted owls. Greater juvenile mass decreased the effect of precipitation, suggesting that greater mass was important for juveniles to maintain homeostasis during fledgling. 5. Feather corticosterone in juvenile spotted owls provided insights to the challenges faced during early development, adding to our understanding of spotted owl life history and potential for population recovery.

opencc-zeroMay 2022View details →

Breeding status shapes territoriality and vocalization patterns in spotted owls

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.

opencc-zeroJul 2022View details →

Data from: Large trees and forest heterogeneity facilitate prey capture by California spotted owls

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 <a name="_Hlk99628060"></a>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: (i) in areas with more large-tree forest, (ii) in areas with more medium trees/medium canopy forest, and (iii) 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 landscapes 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.

opencc-zeroJan 2022View details →

Pairing functional connectivity with population dynamics to prioritize corridors for Southern California spotted owls

Aim: Land use change, climate change, and shifts to disturbance regimes make successful wildlife management challenging, particularly when ongoing urbanization constrains habitat and movement. Preserving and maintaining landscape connectivity is a potential strategy to support wildlife responding to these stressors. Using a novel model framework, we determined the population-level benefit of a set of identified potential corridors for spotted owl population viability. Location: Southern California, United States. Methods: Combining habitat suitability and dynamic metapopulation models, we compared the benefit of corridors to the Southern California spotted owl population, measured as the increase in the expected minimum abundance, both now and under a future climate. Our approach considered key corridor characteristics important to conservation decisions, namely, corridor irreplaceability and local population network benefit. Results: We identified two corridors likely to increase Southern California spotted owl expected minimum abundance under current climate conditions. At the regional scale, of the 16 corridors evaluated, one corridor was irreplaceable (i.e. no other corridors in the network could provide a similar increase in abundance when the irreplaceable corridor was removed) and one corridor was identified as redundant (i.e. remaining corridors in the network can provide some of the increases in abundance offered by the removed corridor). Both putative corridors connected two large, populous, and similarly-sized patches. Additionally, we identified two more corridors at the local scale. We found that, under climate change, population declines may limit the benefit of connectivity for a range-restricted species like the spotted owl. Main Conclusions: Our analytical approach highlights important criteria for corridor identification and prioritization, namely, irreplaceability versus redundancy, local versus regional benefit, and corridor impact in a changing landscape. With the capability of incorporating estimated functional connectivity into population dynamics, our modeling framework advances connectivity decision making for other species of conservation concern and archetypal taxa within ecological communities.

publicMay 2022View details →

Breeding status shapes territoriality and vocalization patterns in spotted owls

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publicJul 2022View details →

Data from: Large trees and forest heterogeneity facilitate prey capture by California spotted owls

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publicJul 2021View details →

Pairing functional connectivity with population dynamics to prioritize corridors for Southern California spotted owls

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publicNov 2021View details →

Feather corticosterone reveals developmental challenges in a long‐term study of juvenile northern spotted owls

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Supplementary material 4 from: Jones GM, Gutiérrez RJ, Kramer HA, Tempel DJ, Berigan William J, Whitmore Sheila A, Peery MZ (2019) Megafire effects on spotted owls: elucidation of a growing threat and a response to Hanson et al. (2018). Nature Conservation 37: 31-51. https://doi.org/10.3897/natureconservation.37.32741

: Data type: Representative photographs of two spotted owl nest areas burned at high fire severity during the King Fire (2014) and three general areas within the Eldorado Study Area in the central Sierra Nevada, California, USA that depict three general fire severity classes of this fire.

Supplementary material 2 from: Jones GM, Gutiérrez RJ, Kramer HA, Tempel DJ, Berigan William J, Whitmore Sheila A, Peery MZ (2019) Megafire effects on spotted owls: elucidation of a growing threat and a response to Hanson et al. (2018). Nature Conservation 37: 31-51. https://doi.org/10.3897/natureconservation.37.32741

Supplementary material 6 from: Jones GM, Gutiérrez RJ, Kramer HA, Tempel DJ, Berigan William J, Whitmore Sheila A, Peery MZ (2019) Megafire effects on spotted owls: elucidation of a growing threat and a response to Hanson et al. (2018). Nature Conservation 37: 31-51. https://doi.org/10.3897/natureconservation.37.32741

Supplementary material 3 from: Jones GM, Gutiérrez RJ, Kramer HA, Tempel DJ, Berigan William J, Whitmore Sheila A, Peery MZ (2019) Megafire effects on spotted owls: elucidation of a growing threat and a response to Hanson et al. (2018). Nature Conservation 37: 31-51. https://doi.org/10.3897/natureconservation.37.32741

Supplementary material 1 from: Jones GM, Gutiérrez RJ, Kramer HA, Tempel DJ, Berigan William J, Whitmore Sheila A, Peery MZ (2019) Megafire effects on spotted owls: elucidation of a growing threat and a response to Hanson et al. (2018). Nature Conservation 37: 31-51. https://doi.org/10.3897/natureconservation.37.32741

Supplementary material 5 from: Jones GM, Gutiérrez RJ, Kramer HA, Tempel DJ, Berigan William J, Whitmore Sheila A, Peery MZ (2019) Megafire effects on spotted owls: elucidation of a growing threat and a response to Hanson et al. (2018). Nature Conservation 37: 31-51. https://doi.org/10.3897/natureconservation.37.32741