Laserfiche WebLink
Natural Resources Assessment <br />P125 Gravel Mine - Southwest of State Highway 66 and County Road 17 <br />Weld County, Colorado <br /> <br />ERO Project #24-180 14 <br />ERO Resources Corporation <br />Western Burrowing Owl <br />Species Background <br />The western burrowing owl (burrowing owl) is a small migrant owl listed by the state of Colorado as a <br />threatened species and is federally protected under the Migratory Bird Treaty Act (MBTA). Primary <br />threats to the burrowing owl include habitat loss and fragmentation, anthropogenic sources of mortality <br />such as vehicular collisions, and loss of wintering grounds, largely in Mexico (McDonald, Korfanta, and <br />Lantz 2004). <br />In general, burrowing owls are found in grasslands with vegetation less than 4 inches high and a <br />relatively large proportion of bare ground (Gillihan and Hutchings 2000). In Colorado, burrowing owls <br />are usually associated with black-tailed prairie dog colonies (Andrews and Righter 1992). More than 70 <br />percent of sightings reported in Colorado Breeding Bird Atlases were in prairie dog colonies (Colorado <br />Bird Atlas Partnership 2016). <br />Burrowing owls usually arrive on their breeding grounds around mid-March to early April and remain <br />until September (Haug and Oliphant 1990). Burrowing owls are typically present in Colorado from March <br />15 through October 31, with breeding from mid-April through early/mid-August (Andrews and Righter <br />1992; Colorado Bird Atlas Partnership 2016). CPW suggests conducting burrowing owl clearance surveys <br />in prairie dog towns that are subject to poisoning or construction projects during the period from March <br />15 through October 31 (CPW 2020). <br />Suitable Habitat and Effects <br />The prairie dog burrows in and adjacent to the project area are suitable habitat for burrowing owls. <br />Inadvertent killing of burrowing owls could occur during prairie dog poisoning, construction, or other <br />earthmoving projects during the breeding period, as well as up to a month before egg laying and several <br />months after young have fledged. CPW has a recommended buffer of 660 feet (0.125 mile) surrounding <br />active burrowing owl nests during the nesting season (March 15 through August 31) (CPW 2020). <br />Burrowing owls could be impacted by the project if work would occur within CPW’s recommended 660- <br />foot buffer of any active burrows. <br />Recommendations <br />A burrowing owl survey should be conducted if work would occur within the recommended buffer of <br />any burrow from March 15 through October 31. Additionally, CPW recommends conducting burrowing <br />owl clearance surveys in prairie dog towns that are subject to poisoning or construction projects during <br />this period (March 15 through October 31) (CPW 2020). If owls are present within 660 feet of the project <br />area, activities should be restricted until the owls have migrated from the site, which can be determined <br />through monitoring. The prairie dog colony that is separated from the project area by St. Vrain Creek <br />and its riparian corridor may have enough visual separation from the project area for burrowing owl <br />surveys to not be required at this location even though these burrows are within 660 feet of the project <br />area. Construction occurring from November 1 through March 14 would not require clearance surveys.