In 2018 the WAfLS project expanded to eight western states. Throughout those states, a large group of volunteers sampled a broad geography. The abundance estimates and habitat associations results from this effort provide critical insight to land managers across the western United States to influence species-specific general conservation actions. CLICK HERE TO VIEW PDF.
2018 Western Asio flammeus Landscape Study (WAfLS) Annual Report
Robert A. Miller (a,1), Carie Battistone (b), Heather Hayes (a), Matt D. Larson (c), Cris Tomlinson (d), Ellie Armstrong (e), Neil Paprocki (f), Joseph B. Buchanan (g), Zoë Nelson (h), Jay D. Carlisle (a), and Colleen Moulton (i)
a Intermountain Bird Observatory, Boise, Idaho, USA;
b California Department of Fish and Wildlife, Sacramento, California, USA;
c Owl Research Institute, Missoula, Montana, USA;
d Nevada Department of Wildlife, Las Vegas, Nevada, USA;
e Klamath Bird Observatory, Medford, Oregon USA;
f HawkWatch International, Salt Lake City, Utah, USA;
g Washington Department of Fish and Wildlife, Olympia, Washington, USA;
h Biodiversity Institute, Laramie, Wyoming, USA;
i Idaho Department of Fish and Game, Boise, Idaho, USA
1 Correspending author: RobertMiller7@boisestate.edu; 208-860-4944
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. Following Booms et al. (2014), who proposed six conservation actions for this species, we set forth to address four of these objectives within the Western Asio flammeus Landscape Study (WAfLS) program: 1) better define and protect important habitats; 2) improve population monitoring; 3) better understand owl movements; and 4) develop management plans and tools. Population monitoring of Short-eared Owls is complicated by the fact that the species is an irruptive breeder with low site fidelity, resulting in large 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 622 participants, many of which were citizen-scientist volunteers, to survey at study sites embedded over 87 million ha within the states of California, Idaho, Montana, Nevada, Oregon, Utah, Washington, and Wyoming during the 2018 breeding season. We surveyed 368 transects, 331 of which were surveyed twice, and detected Short-eared Owls on 57 transects. We performed multi-scale occupancy modeling and maximum entropy modeling to identify population status, habitat and climate associations. Our estimated occupancy rates suggest an increase in abundance in Idaho and Nevada as compared with 2017, and a continuing decrease in abundance in Utah and Wyoming. These numbers and the newly established estimates in other states will help us to put future changes into perspective. As expected, our occupancy modeling found that the probability of detecting Short-eared Owls was impacted by day of the year, time of the survey and local wind conditions. We most often found Short-eared Owls in stubble agriculture areas with lower levels of grazing. Cropland at the transect scale was a large predictor in site occupancy. Consistent with recent years our MaxEnt analysis found Short-eared Owls were more likely in areas of shrubland, cropland, and marshland, and grassland. Our results continue to find that Short-eared Owls have a climate association that puts them at great future risk, primarily their apparent preference of landscapes with higher relative precipitation and moderate seasonality. As our summers continue to become drier, as is expected under most climate scenarios, we would expect a further decrease in the population of this species, possibly through the climate’s effect on prey abundance. As a result of the consistent implementation of this program within Idaho and Utah, we have established with high confidence that the breeding density of Short-eared Owls in 2018 was lower than 2015 and 2016 within these states, yet has increased in Idaho over levels measured in 2017. Lastly, our results demonstrate the feasibility, efficiency, and effectiveness of utilizing public participation in scientific research (i.e., citizen scientists) to achieve a robust sampling methodology across the broad geography of the western United State. We look forward to the continued implementation of this program in future years.