Assessing Feasibility of Mitigating Barn Owl-Vehicle Collisions in Southern Idaho

Large numbers of barn owls are killed along roads in southern Idaho. Although barn-owl vehicle collisions are not unique to Idaho, I-84 has among the world’s highest rates of vehicle-caused mortality for barn owls. This is concerning because much lower rates have caused local extirpation in some areas. Barn owl populations have declined in portions of their range such that regulatory agencies consider them a species of concern, threatened, or endangered in some states, provinces, and countries. This research was designed to understand the spatial, road geometric, and biotic (land cover and prey) factors associated with barn owl-vehicle collisions and examine feasibility of mitigation. The authors also provide a literature review of barn owl road mortality and mitigation approaches from North America and Europe. The greatest rates of mortality along I-84 occurred between Bliss and Hazelton, Idaho. Mortality increased when the highway was close to the Snake River Canyon, close to dairies (agriculture), and farther from water features, and when there were fewer nearby roads, narrower medians, fewer human structures, and a higher percentage of cultivated crops. Owl road kills were higher when plant cover type in the median and right-of-way was grass rather than shrubs. The research team recommends that mortality hotspots be the focus of initial mitigation. Efforts to reduce barn owl mortality should focus on vegetation management in the right-of-way to promote tall shrubs or scrub vegetation to reduce “huntability” for owls, and keeping grassy areas to very low heights to potentially reduce abundance of small mammals through decreased food and cover for them. There should also be development of barriers (hedges or trees, nets, fences, berms or other) to restrict low flight by owls in mortality hotspots. Reducing wildlife-vehicle collisions involving barn owls is an important step in ensuring persistence of this avian species. In so doing, it would reduce chances that the conservation status of barn owls is elevated, which would bring heightened regulatory challenges to the transportation sector in Idaho.

  • Record URL:
  • Supplemental Notes:
    • Cover date: November 2015.
  • Corporate Authors:

    Boise State University

    Department of Biological Sciences
    Science Bldg Room 107
    Boise, Idaho  United States  83725

    Idaho Transportation Department

    Division of Engineering Services, Contracting Services, Research Program
    PO Box 7129
    Boise, ID  United States  83707-7129

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Belthoff, Jim
    • Arnold, Erin
    • Regan, Tempe
    • Allen, Tiffany
    • Kociolek, Angela
  • Publication Date: 2015-12


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 147p

Subject/Index Terms

Filing Info

  • Accession Number: 01596676
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-ID-15-226, RP-226
  • Created Date: Apr 4 2016 12:03PM