Using passive acoustic monitoring to estimate northern spotted owl landscape use and pair occupancy

Abstract

Managing forests for biodiversity conservation while maintaining economic output is a major challenge globally and requires accurate and timely monitoring of imperiled species. In the Pacific Northwest, USA, forest management is heavily influenced by the status of northern spotted owls (Strix occidentalis caurina), which have been in continued population decline for the past four decades. The monitoring program for northern spotted owls is transitioning from mark-resight surveys to a passive acoustic framework, requiring development of alternative analysis approaches. To maintain relevance for conservation and management, these analyses must accurately track underlying population changes, identify responses to disturbance, and estimate occupancy of owl pairs. We randomly selected and surveyed 5-km 2 hexagons for 6 weeks using passive acoustic monitoring in the Olympic Peninsula of Washington and the Oregon Coast Range during the 2018 spotted owl breeding season. We used a convolutional neural network to identify spotted owl calls, followed by logistic regression to determine the sex of vocalizing owls to assign pair status. We implemented multistate occupancy models to estimate probabilities of detection, species-level landscape use, and pair occupancy of spotted owls.We also quantified detections of barred owls (Strix varia), a congeneric competitor and important driver of spotted owl population declines. The overall rate of hexagon use by spotted owls was estimated at 0.21 (SD 0.04) after adjusting for imperfect detection, and pair occupancy was 0.07 (SD 0.02). The probability of detecting a pair (i.e., both female and male) during a weekly occasion was relatively low (0.03, SD 0.01), indicating that true pair occupancy was between 1.3 and 4.1 times greater than the proportion of hexagons with observed pair detections. Barred owls were ubiquitous, with a naïve occupancy rate of 0.97. The intensity of calling by barred owls had a weak, negative effect on the probability of spotted owls being paired when present but had little measurable effect on their detectability. This work establishes a framework that may be effective for spotted owl population monitoring and illustrates that

An integrated passive acoustic monitoring and deep learning pipeline for black‐and‐white ruffed lemurs (Varecia variegata) in Ranomafana National Park, Madagascar

“…By using PAM, primatologists can obtain long‐term, noninvasive data for multiple primate species in an area simultaneously. Such presence/absence data, in combination with geospatial variables, could then be used to generate occupancy and species distribution models (Appel et al, 2023; Campos‐Cerqueira & Aide, 2016; Kalan et al, 2015). PAM can also yield important insights beyond simple presence metrics; for example, without PAM we would not have quantitative evidence of or patterns in ruffed lemur nocturnal vocal activity.…”

Audio tagging of avian dawn chorus recordings in California, Oregon and Washington

“…The transition to the second monitoring phase marks a potential watershed moment for conserving and managing forested lands in the Pacific Northwest. Spotted owl conservation and management objectives continue to be met ( Duchac et al 2020 , Appel et al 2023 , Weldy et al 2023 ), while simultaneously providing valuable multispecies acoustic monitoring data for other objectives, such as monitoring other old-forest-associated species identified in the NWFP, supporting other state and national conservation directives (such as the National Forest Management Act; 94th Congress 2nd Session (1976) ), complementing strategic conservation planning efforts ( Law et al 2021 ) and contributing to global biodiversity conservation and monitoring efforts ( IPBES 2018 , Conference of the Parties to the Convention on Biological Diversity 2022 ).…”

Anthropogenic noise in terrestrial Antarctica: a short review of background information, challenges and opportunities

“…Acoustic monitoring in terrestrial environments has been extensively used in different parts of the world to assess biodiversity (Marques et al 2013;Stevenson et al 2021), to monitor the status and trends of animal populations (Law et al 2018;Appel et al 2023) and to identify and monitor sources of anthropogenic noise (Blumstein et al 2011;Gibb et al 2019). Although the range of ecosystems covered by these studies has been expanding, polar regions continue to be underrepresented, and this is particularly so for Antarctica.…”