Variation in inbreeding rates across the range of Northern Spotted Owls (<i>Strix occidentalis caurina</i>): Insights from over 30 years of monitoring data

Miller, Mark P.; Haig, Susan M.; Forsman, Eric D.; Anthony, Robert G.; Diller, Lowell V.; Dugger, Katie M.; Franklin, Alan B.; Fleming, Tracy L.; Gremel, Scott A.; Lesmeister, Damon B.; Higley, J. Mark; Herter, Dale R.; Sovern, Stan G.

doi:10.1642/auk-18-1.1

Cited by 4 publications

(5 citation statements)

References 47 publications

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“…We found strong evidence that northern spotted owl site occupancy is declining range-wide and that the species is at immediate risk of extirpation from large portions of its geographic range. This finding is not unique to this study (Dugger et al, 2016;Franklin et al, 2021;Yackulic et al, 2019), and other research has pointed to evidence of an extinction vortex (Gilpin & Soulé, 1986) for northern spotted owls (Franklin et al, 2021;Jenkins et al, 2021;Miller et al, 2018).…”

Section: Discussioncontrasting

confidence: 52%

“…As vertebrate populations decline to only a few individuals an extinction vortex can occur in which positive feedbacks occur among environmental and demographic stochasticity, inbreeding, and disrupted behaviors (Gilpin & Soulé, 1986 ), resulting in rapid progression to extinction in just a few years (Fagan & Holmes, 2006 ). Several recent papers have documented factors characteristic of an extinction vortex in northern spotted owl populations, including small population size (Franklin et al, 2021 ), increased rates of inbreeding (Miller et al, 2018 ), and destabilized dispersal dynamics (Jenkins et al, 2021 ). If these trends continue, it is conceivable the northern spotted owl will become extirpated throughout large portions of its range in the next decade.…”

Section: Discussionmentioning

confidence: 99%

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Range‐wide sources of variation in reproductive rates of northern spotted owls

Rockweit

Jenkins

Hines

et al. 2022

Ecological Applications

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We conducted a range‐wide investigation of the dynamics of site‐level reproductive rate of northern spotted owls using survey data from 11 study areas across the subspecies geographic range collected during 1993–2018. Our analytical approach accounted for imperfect detection of owl pairs and misclassification of successful reproduction (i.e., at least one young fledged) and contributed further insights into northern spotted owl population ecology and dynamics. Both nondetection and state misclassification were important, especially because factors affecting these sources of error also affected focal ecological parameters. Annual probabilities of site occupancy were greatest at sites with successful reproduction in the previous year and lowest for sites not occupied by a pair in the previous year. Site‐specific occupancy transition probabilities declined over time and were negatively affected by barred owl presence. Overall, the site‐specific probability of successful reproduction showed substantial year‐to‐year fluctuations and was similar for occupied sites that did or did not experience successful reproduction the previous year. Site‐specific probabilities for successful reproduction were very small for sites that were unoccupied the previous year. Barred owl presence negatively affected the probability of successful reproduction by northern spotted owls in Washington and California, as predicted, but the effect in Oregon was mixed. The proportions of sites occupied by northern spotted owl pairs showed steep, near‐monotonic declines over the study period, with all study areas showing the lowest observed levels of occupancy to date. If trends continue it is likely that northern spotted owls will become extirpated throughout large portions of their range in the coming decades.

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Section: Discussioncontrasting

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Range‐wide sources of variation in reproductive rates of northern spotted owls

Rockweit

Jenkins

Hines

et al. 2022

Ecological Applications

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“…Disturbance in our study areas was primarily associated with timber harvest and thinning operations, but also included wildfire and insect outbreaks. The annual disturbance maps were created using Landsat data and ensemble LandTrendr methodology (Kennedy et al 2010, 2018. These maps capture the year, severity, duration (number of years), and extent of disturbance events at 30-m resolution.…”

Section: Potential Factors Affecting Breeding Dispersalmentioning

confidence: 99%

“… 2016 ) and increased inbreeding rates (Miller et al. 2018 ). Continued population declines have underscored the increasing vulnerability of spotted owls to extirpation.…”

Section: Introductionmentioning

confidence: 99%

“…The northern spotted owl (Strix occidentalis caurina) is a long-lived, philopatric species that requires high canopy cover, large trees, and complex forest structure in core-use areas of their territories (see review by Lesmeister et al 2018). The population demography of this subspecies has been studied over a large geographic area for the past three decades, revealing significant declines in populations and genetic diversity (Funk et al 2010, Dugger et al 2016) and increased inbreeding rates (Miller et al 2018). Continued population declines have underscored the increasing vulnerability of spotted owls to extirpation.…”

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confidence: 99%

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Conspecific and congeneric interactions shape increasing rates of breeding dispersal of northern spotted owls

Jenkins

Lesmeister

Forsman

et al. 2021

Ecological Applications

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Breeding dispersal, the movement from one breeding territory to another, is rare for philopatric species that evolved within relatively stable environments, such as the old-growth coniferous forests of the Pacific Northwest. While dispersal is not inherently maladaptive, the consequences of increased dispersal on population dynamics in populations whose historical dispersal rates are low could be significant, particularly for a declining species. We examined rates and possible causes of breeding dispersal based on a sample of 4,118 northern spotted owls (Strix occidentalis caurina) monitored in seven study areas over 28 years, 1990 to 2017, in Oregon and Washington, USA. Using a multistate mark-resight analysis, we investigated the potential impacts of an emergent congeneric competitor (barred owl Strix varia) and forest alteration (extrinsic factors), and social and individual conditions (intrinsic factors) on 408 successive and 1372 non-successive dispersal events between years. The annual probability of breeding dispersal increased for individual owls that had also dispersed in the previous year and decreased for owls on territories with historically high levels of reproduction.Intrinsic factors including pair status, prior reproductive success, and experience at a site, were also associated with breeding dispersal movements. The percent of monitored owls dispersing each year increased from ~7% early in the study to ~25% at the end of the study, which coincided with a rapid increase in numbers of invasive and competitively dominant barred owls. We suggest that the results presented here can inform spotted owl conservation efforts as we identify factors contributing to changing rates of demographic parameters including site fidelity and breeding dispersal. Our study further shows that increasing rates of breeding dispersal associated with population declines contribute to population instability and vulnerability of northern spotted owls to extinction, and the prognosis is unlikely to change unless active management interventions are undertaken.

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Range-wide declines of northern spotted owl populations in the Pacific Northwest: A meta-analysis

Franklin

Dugger

Lesmeister

et al. 2021

Biological Conservation

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Variation in inbreeding rates across the range of Northern Spotted Owls (Strix occidentalis caurina): Insights from over 30 years of monitoring data

Abstract: Inbreeding has been difficult to quantify in wild populations because of incomplete parentage information. We applied and extended a recently developed framework for addressing this problem to infer inbreeding rates

Cited by 4 publications

References 47 publications

Range‐wide sources of variation in reproductive rates of northern spotted owls

Range‐wide sources of variation in reproductive rates of northern spotted owls

Conspecific and congeneric interactions shape increasing rates of breeding dispersal of northern spotted owls

Range-wide declines of northern spotted owl populations in the Pacific Northwest: A meta-analysis

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