Dugway Proving Ground (DPG), located in west-central Utah, is a Department of Defense (DoD) test site for chemical and biological defensive testing; it is also home to multiple breeding pairs of golden eagles (Aquila chrysaetos). The presence of an eagle nest has the potential to stop military testing and training due to potential nest disturbance. It is vital to DPG and similar DoD installations to fully understand the status of in-use eagle nests on military lands. Using Unmanned Aircraft Systems (UAS) and Small Unmanned Aircraft Systems (sUAS), it may be possible to obtain accurate status updates of eagle nests on DoD lands more efficiently than can be accomplished on foot. The DPG Team designed a blind study conducting weekly golden eagle nFest surveys on DPG to compare the effectiveness of sUAS, UAS, and ground observers.

The DPG Team conducted weekly golden eagle nest surveys on DPG during the 2019 and 2020 nesting seasons, using a blind study design, to compare the effectiveness of three “survey systems”: 1) a ground-based human observer, 2) a commercially available small Unmanned Aircraft System (sUAS; DJI Matrice M600 and E Mergent RC E900), and 3) a military-grade UAS platform (MQ-1C Gray Eagle).

No single platform was clearly superior across all seasons and periods of observation. During the 2019 season, the sUAS observation team proved the most efficient at locating in-use and unknown nests, but it was more expensive than the ground observer (annual operation cost of approx. $130k for the sUAS, versus $20k for the ground observer). The UAS team did not observe frequently enough to be directly compared but appeared to be most efficient observing well-known nests with lots of metadata to reference. UAS costs were not directly assessed, as they operate as part of a larger installation program. Results differed significantly during the 2020 season after the sUAS platform used in 2019 was prohibited from use under the FY19 National Defense Authorization Act. In 2020, the sUAS team had trouble locating nests or identifying status due to the change in platform/payload and was not as efficient as the ground observer. The results indicate that the use of an sUAS is effective but may not yet be able to cost-effectively replace ground monitoring. For instances where the nests are too high or terrain too rugged, sUAS are especially effective. As the cost of the sUAS system is reduced and the policy surrounding flying sUAS in DoD airspace is streamlined, it may become cost-effective compared to on-the-ground monitoring.

A major implementation issue with the use of sUAS in DoD airspace involves obtaining an Airworthiness Release and Exemption to Policy. Both approvals take time to develop, review, and obtain approval. Good metadata and a member of the team that has experience with eagle behavior and good knowledge of the territory is key to obtaining useful data. The UAS observation method was the most uncertain and it proved to be unreliable as a method of weekly nest observations due to scheduling and payload restrictions. If the nest location was well known, the UAS was by far the fastest and most efficient observation method. However, the nature of the platform’s flight and approach patterns made detailed nest metadata critical to the success of the survey.