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Sage Thrasher Nesting Habitat Mapping in Southern B.C.

Mapping Critical Habitat for Sage Thrashers Using Unmanned Aerial Vehicles to Enhance Monitoring and Management for the Canadian Wildlife Service:

The Sage Thrasher (Oreoscoptes montanus) is an Endangered species and is considered one of the rarest birds in Canada. This secretive mimic depends on the protective thickets of large sagebrush (Artemisia tridentata) in which it hides its nests. Sage Thrasher habitats have been lost throughout North America due to land conversion to agriculture. As part of efforts to conserve this species, the Canadian Wildlife Service (CWS) initiated a pilot study to investigate the efficacy of using unmanned aerial vehicles (UAVs) to map and monitor critical sage thrasher nesting habitat.

Sage Thrashers build their nests, like this one, in large sagebrushes. Photo Credit: Jacqueline Dougherty @itsajackiel on Instagram, with permission.

Sage Thrashers build their nests, like this one, in large sagebrushes. Photo Credit: Jacqueline Dougherty @itsajackiel on Instagram, with permission.

Fiera Biological partnered with SRS Avimetrics (SRS) to complete the work within the extreme time and budgetary constraints required. SRS had a suitable UAV system to collect the required imagery, and were based near the study area, so it made logistical sense that they take on the UAV imagery collection part of the project. They deployed their UAV in March of 2017 and captured a series of overlapping aerial images over known sage thrasher nesting sites. Since Fiera had the computer processing power, and remote sensing expertise to manage the monstrous high resolution data files that UAVs are capable of producing, the data was packed up and sent to us via courier. We processed the imagery to derive 3D point-cloud data, which we then used to separate terrain features from vegetation features to discriminate individual sagebrushes that meet known Sage Thrasher nesting criteria. This analysis resulted in the production of map layers that identify sagebrush position, height, and breadth, allowing for classification of habitat quality at varying scales, and has the potential to advance quantitative analysis of sage thrasher habitat suitability, and inform management of critical habitat for this endangered species.

Sage Thrasher, habitat, habitat classification, habitat modeling, UAV, Drone, Imagery, pix4d, wildlife management, remote sensing, data processing

According to our model, the green polygons are prime Sage Trasher nesting habitat. The yellow are sage brush areas unlikely to support Sage Trasher nesting, and the ‘+’ is a confirmed Sage Thrasher nest site.

The timeline for this project was extremely tight, and the budget was extremely challenging, however, the results have excited everyone involved, and the project team continues to work together to produce and publish a peer reviewed paper on this proof-of-concept work, which we hope will garner support for a larger scale project that will have direct sage thrasher habitat management and monitoring implications.

Key Personnel / Role

Brad Danielson / Project Manager, Data Processing, Habitat Modeling.

Canadian Wildlife Service (CWS)

Project Duration
March, 2017