Short-eared Owl 2020 Annual Report

The Short-eared Owl (Asio flammeus) is an open-country species that breeds in the northern United States and Canada, and has likely experienced a long-term, range-wide population decline. However, the cause and magnitude of the decline are not well understood. Several conservation actions have been proposed for this species (Booms et al. 2014), including: 1) better define and protect important habitats; 2) improve population monitoring; 3) determine seasonal and annual movements; 4) re-evaluate NatureServe’s National Conservation Classifications; and 5) develop management plans and tools. Our program has been largely motivated by these conservation actions.

CLICK HERE to read the 2020 Annual and Comprehensive Report.

Watch a recorded webinar discussing the final results of the project here.


Short-eared Owl Population Size, Distribution, Habitat Use, and Modelled Response to a Changing Climate: 2020 Annual and Comprehensive Report

Robert A. Miller (a,1), Carie Battistone (b), Heather Hayes (a), Courtney J. Conway (c), Andrew Meyers (c), Cody Tisdale (c), Matt D. Larson (d), Joseph G. Barnes (e), Ellie Armstrong (f), John D. Alexander (f), Neil Paprocki (c,g), Annette Hansen (g), Theresa L. Pope (h), Russel Norvell (h), Joseph B. Buchanan (i), Mason Lee (j), Jay D. Carlisle (a), Colleen E. Moulton (k), and Travis L. Booms (l)

a – Intermountain Bird Observatory, Boise, Idaho, USA;
b – California Department of Fish and Wildlife, Sacramento, California, USA;
c – University of Idaho, Moscow, Idaho, USA;
d – Owl Research Institute, Missoula, Montana, USA;
e – Nevada Department of Wildlife, Reno, Nevada, USA;
f – Klamath Bird Observatory, Medford, Oregon USA;
g – HawkWatch International, Salt Lake City, Utah, USA;
h – Utah Division of Wildlife Resources, Salt Lake City, Utah, USA;
i – Washington Department of Fish and Wildlife, Olympia, Washington, USA;
j – Biodiversity Institute, Laramie, Wyoming, USA;
k – Idaho Department of Fish and Game, Boise, Idaho, USA;
l – Alaska Department of Fish and Game, Fairbanks, Alaska, USA

1 – Corresponding author: RobertMiller7@boisestate.edu; 208-860-4944

ABSTRACT

The Short-eared Owl (Asio flammeus) is an open-country species that breeds in the northern United States and Canada and has likely experienced a long-term, range-wide population decline. However, the cause and magnitude of the decline are not well understood. Several conservation actions have been proposed for this species (Booms et al. 2014), including 1) better define and protect important habitats; 2) improve population monitoring; 3) determine seasonal and annual movements; 4) re-evaluate NatureServe’s National Conservation Classifications; and 5) develop management plans and tools. Our program has been largely motivated by these conservation actions. Population monitoring of Short-eared Owls is complicated by the fact that the species is an irruptive breeder with low site fidelity, resulting in annual shifts in local breeding densities, often tied to fluctuations in prey density. It is therefore critical to implement monitoring at a scale needed to detect regional changes in distribution that likely occur annually. We recruited more than 1,200 participants, mostly community-science volunteers to implement a survey of Short-eared Owls across eight western states over the past six years. The study sites were distributed across over 87 million hectares within the states of California, Idaho, Montana, Nevada, Oregon, Utah, Washington, and Wyoming. We found that grazing negatively influenced Short-eared Owl occupancy, but grazing and Short-eared Owls are not mutually exclusive. By managing the grazing utilization rate across the pasture, the negative effect can be at least partially mitigated. Short-eared Owls favor native shrublands and grassland and avoid anthropogenic landscapes. We see no evidence that the steep decline in the species that was suspected to have occurred over the past 40 years has continued. Short-eared Owl occupancy rates were highly variable across the eight states within the program and from year-to-year. However, overall weighted mean occupancy rates were relatively stable. We are unable to answer if these spatial and temporal shifts in occupancy were the result of movement or birth/death rates. Short-eared Owls were more often found in natural versus anthropogenic landscapes, in sagebrush/hay/pasture versus marsh and row crops, and in more grass versus structured land covers. While we regularly detected owls on anthropogenic landscapes, populations in native shrubland and grasslands were more stable; possibly due to more stable prey resources, although other hypotheses exist. As expected, we more often found Short-eared Owls in less rugged areas at lower elevations. Lastly, Short-eared Owls occupied areas that were intermediate, but not too hot during the summer period, and in areas that received more precipitation in the driest season. Our modeling results indicated Short-eared Owls are under extreme threat from common projections of climate change effects. We conservatively predicted that average future viability of Short-eared Owls across our study area will decrease by 59% in the next 50 years. We predicted that the amount of “good” habitat would decrease by 76%, and the amount of “great” habitat would decrease by 60% over that period. Our results demonstrated the feasibility, efficiency, and effectiveness of utilizing public participation in scientific research (i.e., community scientists) to achieve a robust sampling methodology across the broad geography of the western United States.

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