Up, Up and Count

Tern collage
Both the Aleutian tern, top, and the Arctic tern have breeding grounds at Kenai National Wildlife Refuge in Alaska. Historically, getting an accurate bird count has been challenging. New technology is helping to solve the problem. (Photos: USFWS)

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.



Mark Laker at Kenai nwr
Refuge ecologist Mark Laker operates an unmanned aircraft at Kenai Refuge in Alaska. (Photo: Tracy Swerm)


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:

  • Finding the optimum UAS settings and flight altitude to tell Aleutian terns from Arctic terns, based on the color of their bills (black in adult breeding Aleutian terns, and red in adult breeding Arctic terns).
  • Documenting nesting phenology — or seasonal timing — to determine the best dates for future bird counts.
  • Assessing whether UAS flights would disturb nesting terns.


Map AleutianTernSurvey
A composite image made from several hundred overlapping photos from a UAS camera offers an aerial view of tern nesting grounds. Red dots show locations of nesting terns. The inset bird images illustrate how clearly the two species could be discerned from the UAS photos: Red beak identifies the adult Arctic tern; black beak and white eye band confirm the adult Aleutian tern. (Photo: USFWS)

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.



The UAS, operated by Kenai Refuge ecologist Mark Laker, standing alongside Kenai Refuge biologist Dom Watts (in red jacket), captured video and still photos of Kenai Refuge and the terns. (Video: USFWS)

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.



Arctic Tern migration map by Andreas Trepte
The Artic tern makes the equivalent of three roundtrips to the moon in its migrating lifetime. Here, its wintering grounds in Antarctica are shown in teal and its northern breeding grounds are shown in red. (Photo: Creative Commons)

“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.”



 Jeff Lucas flying UAS by Scott Bishaw
Jeff Lucas, with the Federal Law Enforcement Training Center in Georgia, is one of 19 certified UAS pilots in the U.S. Fish and Wildlife Service. (Photo: Scott Bishaw)

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.”



Kenai Refuge
Public recreational use of drones is prohibited at Kenai Refuge and other lands within the National Wildlife Refuge System. (Photo: USFWS)

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:

  • UAS are considered aircraft. They also fall under the definition of “motorized equipment” or “mechanical transport.” Therefore, they are prohibited from taking off from, landing in, or being operated from Congressionally-designated Wilderness.
  • UAS are not permitted to fly in certain areas and situations, such as wildfires, when temporary flight restrictions (TFRs) are in place. Search the FAA website for up-to-date information on TFRs
  • Learn more about NOAA’s drone policy regarding marine mammals.
  • Check the website of your state fish and wildlife agency for regulations about the use of drones on lands it manages.


Arctic Tern by Aaron Fellmeth Photography from Creative commos
An adult Arctic tern displays its characteristic red bill. (Photo: Aaron Fellmeth Photography, courtesy Creative Commons)

Arctic Tern Facts:

  • Arctic terns migrate up to 1.5 million miles during their lifetime. That’s the equivalent of  three round trips to the moon.  
  • Arctic terns feed from the water while on the wing and can live up to 34 years.
  • Scientists from the British Antarctic Survey reported that Arctic terns don’t immediately head south from Greenland, but first spend almost a month in the North Atlantic Ocean before continuing down the coast of northwest Africa.


Aleutian tern by Budgora. Creative Commons
The winter range of the Aleutian tern was unknown until the late 1980s. (Photo: Budgora, courtesy Creative Commons)

Aleutian Tern Facts:

  • The Aleutian tern breeds in colonies on coasts and islands in Alaska and eastern Siberia.
  • The Aleutian tern usually nests in small colonies and often with the Arctic tern. Aleutian terns may benefit from nesting with Arctic terns, which are more aggressive in defending their nests.
  • Like most terns, the Aleutian tern feeds by plunge-diving for fish. Part of the courtship display involves a male tern’s offering fish to a female tern.

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.”



Compiled by Martha_Nudel@fws.gov, April 11, 2018