Competitive interactions and resource partitioning between northern spotted owls and barred owls in western Oregon

2014 ◽  
Vol 185 (1) ◽  
pp. 1-50 ◽  
Author(s):  
J. David Wiens ◽  
Robert G. Anthony ◽  
Eric D. Forsman
Keyword(s):  
Resource Partitioning ◽  
Competitive Interactions ◽  
Spotted Owls ◽  
Northern Spotted Owls ◽  
Barred Owls

scholarly journals Social status, forest disturbance, and Barred Owls shape long-term trends in breeding dispersal distance of Northern Spotted Owls

The Condor ◽  
2019 ◽  
Vol 121 (4) ◽  
Author(s):  
Julianna M A Jenkins ◽  
Damon B Lesmeister ◽  
Eric D Forsman ◽  
Katie M Dugger ◽  
Steven H Ackers ◽  
...  
Keyword(s):  
Forest Disturbance ◽  
Dispersal Distance ◽  
Historical Study ◽  
Breeding Dispersal ◽  
Spotted Owls ◽  
Dispersal Distances ◽  
Dispersal Events ◽  
Northern Spotted Owls ◽  
Barred Owls ◽  
Over Time

Abstract Dispersal among breeding sites in territorial animals (i.e. breeding dispersal) is driven by numerous selection pressures, including competition and spatiotemporal variation in habitat quality. The scale and trend of dispersal movements over time may signal changing conditions within the population or on the landscape. We examined 2,158 breeding dispersal events from 694 male and 608 female individually marked Northern Spotted Owls (Strix occidentalis caurina) monitored over 28 yr on 7 study areas to assess the relative importance of individual (sex, experience), reproductive (annual productivity, mate availability), and environmental (forest alteration, presence of competitor) sources of variation in breeding dispersal distance. Median breeding dispersal distance was 3.17 km, with 99% of all breeding dispersal events <37 km. Mean annual dispersal distances increased by 2.43 km in Oregon and 9.40 km in Washington between 1990 and 2017, which coincided with increases in annual detections of nonnative Barred Owl (S. varia). Frequency of breeding dispersal events, both among and within individuals, also increased over time. Female owls moved farther than males (median of 3.26 and 3.10 km, respectively), and birds with less experience (territory tenure) moved farther than those with more experience. Owls that were single in the year prior to dispersal moved 13–31% farther than those paired prior to dispersal. The greatest environmental change occurring over the course of our study was the expansion of Barred Owl populations. Breeding dispersal distance was positively related to Barred Owls in the study area and disturbance within the originating territory. While it appears that social factors continue to be important drivers of breeding dispersal distance in Spotted Owls, increased competition from Barred Owls and habitat alteration have a contributing effect. Increased breeding dispersal distances should be of concern for conservation efforts and considered in population monitoring because changing dispersal behavior may lead to higher rates of mortality and/or emigration from historical study areas.

scholarly journals Does The Presence of Barred Owls Suppress the Calling Behavior of Spotted Owls?

The Condor ◽  
2006 ◽  
Vol 108 (4) ◽  
pp. 760-769 ◽  
Author(s):  
Michelle L. Crozier ◽  
Mark E. Seamans ◽  
R. J. GutiÉRrez ◽  
Peter J. Loschl ◽  
Robert B. Horn ◽  
...  
Keyword(s):  
Calling Behavior ◽  
Field Observations ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Response Data ◽  
Strix Varia ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls ◽  
Barred Owls

Abstract Abstract Barred Owls (Strix varia) have expanded their range throughout the ranges of Northern (Strix occidentalis caurina) and California Spotted Owls (S. o. occidentalis). Field observations have suggested that Barred Owls may be behaviorally dominant to Spotted Owls. Therefore, we conducted a test of behavioral dominance by assessing responsiveness of Spotted Owls to conspecific calls when they were in the simulated presence (i.e., imitation of Barred Owl vocalizations) of a Barred Owl. We hypothesized that Spotted Owls would be less likely to respond to conspecific calls in areas where Barred Owls were common. We used a binary 2 × 2 crossover experimental design to examine male Spotted Owl responses at 10 territories randomly selected within two study areas that differed in abundance of Barred Owls. We also conducted a quasi experiment at four study areas using response data from any Spotted Owl (male or female) detected following exposure to Barred Owl calls. We inferred from the crossover experiment that the simulated presence of a Barred Owl might negatively affect Spotted Owl responsiveness. Both subspecies of Spotted Owl responded less to Spotted Owl calls after exposure to Barred Owl calls, Northern Spotted Owls responded less frequently in areas having higher numbers of Barred Owls, and California Spotted Owls responded less frequently than Northern Spotted Owls overall.

scholarly journals Barred owls and landscape attributes influence territory occupancy of northern spotted owls

2014 ◽  
Vol 78 (8) ◽  
pp. 1436-1443 ◽  
Author(s):  
Stan G. Sovern ◽  
Eric D. Forsman ◽  
Gail S. Olson ◽  
Brian L. Biswell ◽  
Margaret Taylor ◽  
...  
Keyword(s):  
Spotted Owls ◽  
Northern Spotted Owls ◽  
Barred Owls ◽  
Territory Occupancy ◽  
Landscape Attributes

A synopsis of suggested approaches to address potential competitive interactions between Barred Owls (Strix varia) and Spotted Owls (S. occidentalis)

2007 ◽  
Vol 9 (6) ◽  
pp. 679-691 ◽  
Author(s):  
Joseph B. Buchanan ◽  
R. J. Gutiérrez ◽  
Robert G. Anthony ◽  
Tim Cullinan ◽  
Lowell V. Diller ◽  
...  
Keyword(s):  
Competitive Interactions ◽  
Strix Varia ◽  
Spotted Owls ◽  
Barred Owls

Bringing Ethics to Wild Lives: Shaping Public Policy for Barred and Northern Spotted Owls

2018 ◽  
Vol 26 (2) ◽  
pp. 217-238 ◽  
Author(s):  
William S. Lynn
Keyword(s):  
Public Policy ◽  
The United States ◽  
Habitat Destruction ◽  
Stakeholder Group ◽  
Policy Dialogue ◽  
Spotted Owls ◽  
Key Factor ◽  
First Time ◽  
Northern Spotted Owls ◽  
Barred Owls

Abstract Ethics reviews are not part of environmental policy or wildlife management in the United States. This changed when, for the first time, the US Fish and Wildlife Service conducted such a review with respect to the barred and northern spotted owls. Spotted owls are endangered throughout their range by a variety of anthropogenic and natural forces. The interspecific competition between barred and spotted owls is a key factor second only to habitat destruction. A proposed lethal experiment to remove barred owls raised ethical concerns among wildlife agencies, citizens, and advocacy groups. Seeking to better understand these concerns, the Service created the Barred Owl Stakeholder Group. Using an innovative method and instrument in the form of an ethics-based policy dialogue and an ethics brief, the stakeholder group explored the ethical dimensions of the removal experiment. This process holds lessons for how public policy can bring ethics to bear on wild lives.

scholarly journals Passive acoustic monitoring effectively detects Northern Spotted Owls and Barred Owls over a range of forest conditions

The Condor ◽  
2020 ◽  
Vol 122 (3) ◽  
Author(s):  
Leila S Duchac ◽  
Damon B Lesmeister ◽  
Katie M Dugger ◽  
Zachary J Ruff ◽  
Raymond J Davis
Keyword(s):  
Acoustic Monitoring ◽  
Survey Method ◽  
Passive Acoustic Monitoring ◽  
Spotted Owl ◽  
Detection Probabilities ◽  
Spotted Owls ◽  
Northern Spotted Owl ◽  
Passive Acoustic ◽  
Northern Spotted Owls ◽  
Barred Owls

Abstract Passive acoustic monitoring using autonomous recording units (ARUs) is a fast-growing area of wildlife research especially for rare, cryptic species that vocalize. Northern Spotted Owl (Strix occidentalis caurina) populations have been monitored since the mid-1980s using mark–recapture methods. To evaluate an alternative survey method, we used ARUs to detect calls of Northern Spotted Owls and Barred Owls (S. varia), a congener that has expanded its range into the Pacific Northwest and threatens Northern Spotted Owl persistence. We set ARUs at 30 500-ha hexagons (150 ARU stations) with recent Northern Spotted Owl activity and high Barred Owl density within Northern Spotted Owl demographic study areas in Oregon and Washington, and set ARUs to record continuously each night from March to July, 2017. We reviewed spectrograms (visual representations of sound) and tagged target vocalizations to extract calls from ~160,000 hr of recordings. Even in a study area with low occupancy rates on historical territories (Washington’s Olympic Peninsula), the probability of detecting a Northern Spotted Owl when it was present in a hexagon exceeded 0.95 after 3 weeks of recording. Environmental noise, mainly from rain, wind, and streams, decreased detection probabilities for both species over all study areas. Using demographic information about known Northern Spotted Owls, we found that weekly detection probabilities of Northern Spotted Owls were higher when ARUs were closer to known nests and activity centers and when owls were paired, suggesting passive acoustic data alone could help locate Northern Spotted Owl pairs on the landscape. These results demonstrate that ARUs can effectively detect Northern Spotted Owls when they are present, even in a landscape with high Barred Owl density, thereby facilitating the use of passive, occupancy-based study designs to monitor Northern Spotted Owl populations.

Barred Owls reduce occupancy and breeding propensity of Northern Spotted Owl in a Washington old-growth forest

The Condor ◽  
2019 ◽  
Vol 121 (3) ◽  
Author(s):  
Anna O Mangan ◽  
Tara Chestnut ◽  
Jody C Vogeler ◽  
Ian K Breckheimer ◽  
Wendy M King ◽  
...  
Keyword(s):  
Endangered Species ◽  
Timber Harvest ◽  
Spotted Owl ◽  
Occupancy Dynamics ◽  
Old Growth Forest ◽  
Spotted Owls ◽  
Northern Spotted Owl ◽  
Northern Spotted Owls ◽  
Barred Owls ◽  
Breeding Propensity

Abstract Protected lands like national parks are important refuges for threatened and endangered species as environmental pressures on wildlife and their habitats increase. The Northern Spotted Owl (Strix occidentalis caurina), a species designated as threatened under the Endangered Species Act, occurs on public lands throughout the western United States including Mount Rainier National Park (MRNP), Washington. With virtually no history of timber harvest or large forest disturbance within MRNP boundaries since the park’s creation in 1899, MRNP provides an ideal place to evaluate potential impacts of climate change and invasive Barred Owls (Strix varia) on the Northern Spotted Owl. We used a multi-state, multi-season occupancy model to investigate how Northern Spotted Owl occupancy dynamics and breeding propensity are related to the presence of Barred Owls, local and regional weather, and habitat characteristics at MRNP from 1997 to 2016. Historical occupancy of Northern Spotted Owl breeding territories in MRNP has declined by 50% in the last 20 yr, and territory occupancy by breeding Northern Spotted Owls also decreased, reaching a low of 25% in 2016. Occupancy rates were higher on territories with steeper terrain and breeding rates were lower when Barred Owls were detected within historical territories. Our results also indicated that breeding propensity was higher when early nesting season temperatures during March and April were higher. In addition, the ability to detect breeding Northern Spotted Owls decreased when Barred Owls were present in the territory. Habitat variables from LiDAR were not correlated with Northern Spotted Owl occupancy dynamics, likely reflecting the dominance of old-growth forest in this protected park. This study illustrates the strong relationship between Barred Owls and Northern Spotted Owl demographics and breeding site selection in a landscape where habitat loss by timber harvest and fire has not occurred.

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