HABITAT ASSESSMENT OF GREAT GRAY OWL (STRIX NEBULOSA YOSEMITENSIS) IN YOSEMITE NATIONAL PARK, CALIFORNIA

Great gray owls (Strix nebulosa yosemitensis) in the Sierra Nevada are a genetically unique subspecies (yosemitensis)with a small population size and corresponding low genetic diversity. Most of this population resides in Yosemite and the habitat within the park is critical to the persistence of the subspecies. Fortunately, recent technological advances have greatly increased our ability to collect wildlife tracking data yielding precise location and movement information. This information will ensure that imminent habitat modifications meet our objectives of (1) improving great gray owl habitat in the park by producing better foraging habitat and (2) making roadsides less attractive to the owls, thereby reducing wildlife-vehicle collisions. Wildlife-vehicle collisions are the most known source of mortality for adult great gray owls in the park. Fine-scale tracking data will enable a better understanding of roadside conditions that attract or repel the owls, thereby designing tree removal to reduce the chance of future owl-vehicle collisions. In meadows, fine-scale data on habitat use can help inform restoration designs to favor optimal owl forage conditions.

My position title is biology assistant and field technician for the Great Gray Owl Project. The project’s goal is to better understand great gray owl nesting and foraging use near roads and reduce owl mortality in Yosemite. Research methods include radio telemetry setup and vegetation protocols for habitat assessment.

Since my first workday (May 22) to my last workday (July 27), I have completed 202 vegetation plots and 101 observation/perch sites recorded from our 4 tagged great gray owls. I learned how to perform radio telemetry setup, VHF tracking, habitat assessment, and observe animals practicing the least invasive method possible. I learned how to complete vegetation protocols for habitat assessment. Through my volunteering in other projects, I was able to learn how to complete owl broadcasting, spotted owl surveys, bird banding, bat netting, and bear roving. Although data analysis is still ongoing, 30% of the perch sites recorded from owls were less than a mile away from a main road. This proves that research like these is important for wildlife conservation and management in national parks and areas where human presence may alter natural behavior.