Abstract Title

Assessing Vocal Activity Patterns of Sympatric Owl Species in Grand Canyon National Park

Additional Funding Sources

This research, conducted at the Raptor Research Experiences for Undergraduates site, was supported by the National Science Foundation and Department of Defense under Grant No. DBI-1852133 and by Boise State University. We also acknowledge support from Grand Canyon National Park Service.

Abstract

Environmental changes in the Anthropocene are causing rapid shifts to species’ distributions, phenology and activity periods worldwide, with unknown consequences on local community dynamics. In stable communities, the time of day when species are active, should minimize their risk of encountering dominant competitors or predators. When species are active should also maximize species’ access to food, as well as their ability to interact with conspecifics. Therefore, knowledge of species’ active times can help quantify potential niche overlap. Our project focused on assessing seasonal and daily vocal activity patterns of three sympatric owl species (Mexican Spotted Owls (Strix occidentalis lucida), Flammulated Owls (Psiloscops flammeolus), and Great Horned Owls (Bubo virginianus) within Grand Canyon National Park. We described daily activity patterns using data collected from 2019, 2020 and 2021 with automated acoustic recorders, placed during the months of March to early July. We detected 53 Mexican Spotted Owls, 34 Flammulated Owls and 14 Great Horned Owl calls from 10 recorders. Seasonal vocal activity patterns were described using reviewed literature. We predicted that owl species that overlap closely in space and breeding season phenology (i.e., other niche axes), were more likely to partition their nightly vocal activity to facilitate their coexistence. Owls vocalize during their breeding season to find mates, defend territories, and communicate with young. Knowledge of vocal activity patterns should facilitate management, guiding when to focus monitoring efforts that rely on auditory detections, and when to minimize disturbance from anthropogenic noises that may disrupt species’ ability to communicate. We discuss how our results can guide monitoring and management of owls that inhabit Grand Canyon National Park.

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Assessing Vocal Activity Patterns of Sympatric Owl Species in Grand Canyon National Park

Environmental changes in the Anthropocene are causing rapid shifts to species’ distributions, phenology and activity periods worldwide, with unknown consequences on local community dynamics. In stable communities, the time of day when species are active, should minimize their risk of encountering dominant competitors or predators. When species are active should also maximize species’ access to food, as well as their ability to interact with conspecifics. Therefore, knowledge of species’ active times can help quantify potential niche overlap. Our project focused on assessing seasonal and daily vocal activity patterns of three sympatric owl species (Mexican Spotted Owls (Strix occidentalis lucida), Flammulated Owls (Psiloscops flammeolus), and Great Horned Owls (Bubo virginianus) within Grand Canyon National Park. We described daily activity patterns using data collected from 2019, 2020 and 2021 with automated acoustic recorders, placed during the months of March to early July. We detected 53 Mexican Spotted Owls, 34 Flammulated Owls and 14 Great Horned Owl calls from 10 recorders. Seasonal vocal activity patterns were described using reviewed literature. We predicted that owl species that overlap closely in space and breeding season phenology (i.e., other niche axes), were more likely to partition their nightly vocal activity to facilitate their coexistence. Owls vocalize during their breeding season to find mates, defend territories, and communicate with young. Knowledge of vocal activity patterns should facilitate management, guiding when to focus monitoring efforts that rely on auditory detections, and when to minimize disturbance from anthropogenic noises that may disrupt species’ ability to communicate. We discuss how our results can guide monitoring and management of owls that inhabit Grand Canyon National Park.