An uncommon bird, the Aleutian tern nests along the Bering Sea in Alaska and migrates to Asia. Its winter range was unknown until the late 1980s. Its relative, the Arctic tern, is known for its 44,000-mile roundtrip migration between its Arctic breeding ground and its wintering grounds off Antarctica — the longest journey of any bird.
Both birds breed near Headquarters Lake, a 15-minute walk from the office of Kenai National Wildlife Refuge. Aleutian terns were first confirmed to be nesting in the lake’s wetlands and shrubs in 2003. By 2013, biologists had identified at least 25 likely Aleutian tern nest locations, with some 40 to 60 birds in the colony. But getting an accurate count has been tough, especially because Aleutian terns may abandon colonies when disturbed.
“Aleutian terns have been surveyed for decades,” says Mark Laker, ecologist at Kenai Refuge. “Traditionally, we have done the surveys on foot to the edge of their breeding grounds.” Getting close enough to pinpoint a nesting tern and its well-camouflaged eggs has been very difficult. Until now.
With a dramatic decline in Aleutian tern populations in recent decades, there’s tremendous interest in getting more information on known populations. Enter unmanned aircraft systems (UAS), better known as drones, which have gained broad use within the Department of the Interior.
DOI has a fleet of 312 unmanned aircraft and flew nearly 5,000 missions in 2017, ranging from fighting wildfires to monitoring dams and spillways and mapping wildlife. A recent report summarizes flights made by more than 200 certified pilots in 32 states.
Kenai Refuge had many objectives for its June 7-21, 2017, UAS tern surveys. First and most important was to estimate the colony size and breeding success of the two species. Other objectives included:
All flights were limited to 13 minutes. The first flew 200 feet above the colony. Other flights went lower to ensure that photos taken by a UAS-mounted camera could be used to distinguish between the two species. “The terns ignored the UAS, and they showed up clearly in the images the drone was taking,” Laker says. At 75 feet above the colony, the terns continued to ignore the flight. No startling, or flushing, of birds occurred.
“I was ready to call it a success,” says Laker. Not so his colleagues, Kenai Refuge biologists Dawn Magness and Todd Eskelin. Determined to collect the very best possible population data, they set the next two flights at 60 feet and then 50 feet above the colony.
All the while, the UAS was taking some 750 photos on a timed basis. “The UAS flies back and forth over the survey area,” Laker says. “It’s a pre-programmed flight so the photos overlap one another by more than 50 percent” to produce an image mosaic. The images are geotagged to identify the latitude, longitude and elevation of the camera when the shots were taken.
By the end of eight surveys, 28 potential nest sites had been identified. Tern locations identified on the images were given digital markers. “Sometimes, when the adult tern was off the nest, we could find a nest by using the digital marker and see individual eggs and chicks,” Laker says.
“The survey results were far superior to what we could have learned if we were doing this survey over 60 acres on foot,” says Laker. “We probably would have had to do several transects” — pre-measured lines laid out for counting purposes — “if we had done this on foot.”
“We did have a couple of terns dive at the UAS during one of the higher flights,” Laker recalls. “But that was right after the terns attacked a bald eagle in the area, and they were agitated.”
Service UAS Pilots Must Be Certified
The first U.S. Fish and Wildlife Service UAS pilots were certified in early 2017. All Service unmanned systems are operated by Federal Aviation Administration-certified pilots, who must complete training programs administered through the Department of the Interior Office of Aviation Services and pass FAA-required tests. The Service has about 19 certified pilots to date; a new training class started in March to add more than a dozen pilots.
The Service has a variety of uses for drones outside Alaska. For example, it uses them to monitor sandhill cranes. It also uses them to ensure that private landowners are meeting conditions for conservation easements.
The UAS is well-suited to bridge the gap between labor-intensive foot surveys and costly flights by private aircraft, says Jeff Lucas, a certified UAS pilot. “Before the UAS program, a field biologist would have to request a manned aircraft, who was often a contractor, to provide aerial imagery. It was expensive. It was time-consuming, and it was complicated.
“Now, with the proper training and equipment, a field biologist can launch a UAS and conduct the survey for a fraction of the cost to taxpayers,” Lucas says. “It takes way less time and involves far less logistical planning.”
Public Use of Drones on Wildlife Refuges
The recreational use of UAS, or drones, by the public on lands within the National Wildlife Refuge System is prohibited under 50 CFR 27.34. Sensitive wildlife is protected on these lands and can be dramatically affected by drone flights. Here are a few tips about flying drones on lands other than national wildlife refuges:
Arctic Tern Facts:
Aleutian Tern Facts:
Next year, Laker and his partners plan to use a thermal camera mounted on a UAS to find tern fledgings hiding in the grass: “We are confident the technology will help in conservation efforts for these globe-trotting birds.”