Publication Type:Government Report
Keywords:Asio flammeus, community science, community scientists, habitat use, occupancy, population trend, Short-eared Owl
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 regional 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 605 participants, many of which were community-scientist volunteers, to survey at study sites embedded over 87 million hectares within the states of California, Idaho, Montana, Nevada, Oregon, Utah, Washington, and Wyoming during the 2019 breeding season. We surveyed 334 transects, 273 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 annual increase in breeding density in the northern and eastern states, most strongly in Montana, followed by Washington, Wyoming, and Utah. Idaho, Nevada, Oregon, and California had lower breeding densities than in 2018. These numbers will help us to put future changes into perspective. We most often found Short-eared Owls at points with complex grassland, fallow agriculture fields, and with lower levels of grazing. In contrast to 2018, this year shrubland landscapes were not favored, likely influenced by the shift in breeding density toward eastern Montana. Transect occupancy was most strongly associated with grasslands, hay, and fallow fields, with orchards and vine crops specifically avoided. 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 expect a further decrease in the population of this species, possibly through the climate’s effect on prey abundance. Our results demonstrate 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. We look forward to the continued implementation of this program in future years and directly influencing conservation actions.
A spreadsheet accompanied the report: 1040 survey points in the Idaho study area from which Short-eared Owl presence/absence findings were recorded during the 2019 field season; the species was seen at 38 of them and was not detected at 1002.
Electronic File - Zoology: Birds
The document is said to be a 2019 annual report, and we are looking at it in December 2019, so it indeed must be from 2019.