Conservation Status: U.S. Fish and Wildlife Service - Bird Species of Conservation Concern
Threats to Survival: Habitat loss and fragmentation; reductions in burrowing mammal populations
Where Have All the Owls Gone?
The western burrowing owl population in San Diego County is at risk of going locally extinct. As a result, our Recovery Ecology team is working with our partners to understand ways to halt and hopefully reverse the owls’ decline. We are studying how many owlets are produced each year, predation and other causes of mortality, and food and habitat needs, all with the aim of helping land managers protect these diminutive and charistmatic raptors. A major cause of the western burrowing owl population decline is the local extirpation of other burrowing animals, such as prairie dogs, badgers, and desert tortoises, which dig the burrows the owls use for nesting and shelter. In San Diego County, the primary burrow builder is the California ground squirrel. Since 2011, our team has been working to develop strategies for reestablishing ground squirrels in protected areas of the county. We have tested and measured the use of translocation to bring squirrels into areas where they have been removed, and modified habitats to encourage natural dispersal in areas that still have remnant populations of squirrels.
Not Just Any Grassland
The burrowing owl is a grassland specialist and requires short open grassland to thrive, but unfortunately intact native grassland is rare in our region. We have been visiting many grassland habitats throughout the county to search for the presence of both squirrels and owls. We are measuring vegetation and soil conditions in order to characterize the areas that support these two species. We are also using this information to prioritize areas for habitat restoration and translocation.
Not All Burrows Are Created Equal
In many parts of the burrowing owls’ range, including San Diego, artificial burrows are used in place of naturally dug burrows. However, unlike natural burrow systems in active squirrel colonies, artificial burrows are not self-sustaining and require costly upkeep and maintenance. Because we do not know if artificial burrows function similarly to natural burrows in meeting the needs of the owls for nesting, we are testing and comparing conditions inside both types of burrows to make recommendations for improving artificial burrows.