For an olive-sided flycatcher, migration can be a marathon. Some of the soot-colored songbirds travel more than 15,000 miles each year, flying from South America to Alaska and then back again. It’s a dizzyingly long journey for a bird that weighs just over an ounce.
“Alaska populations of olive-sided flycatchers are at this thin margin of what is biologically possible,” said Julie Hagelin, a wildlife research biologist with the Alaska Department of Fish and Game and a senior research scientist at the University of Alaska Fairbanks.
To survive long journeys, birds need safe places to rest and refuel. But the locations of these “little utopias” are a mystery, says Dr. Hagelin. So in 2013, he and his colleagues set out to solve it by tracking birds. They hope that identifying critical stopover sites could provide clues about why olive-sided flycatcher populations are declining and what might be needed to save them, including where to -experts target their conservation efforts.
The research proved more difficult than they bargained for. Olive-sided flycatchers often breed in buggy bogs. They perched on top of the trees. And they are elusive, scattered across the landscape and difficult to catch. “After the first year of struggling with this project, it became really clear why no one in their right mind would want to try and study this bird,” said Dr. Hagelin.
Here’s what it took for the scientists to get the data:
Make a charm
Olive-sided flycatchers can be very sensitive to intrusions into their territory, so scientists have lured the birds with fake avian rivals. They bought wood bird decoys on eBay, and then painted white patches on the sides to mimic the flash of white feathers that males often display when they are agitated. “It’s kind of a long distance signal of ‘Go away’ or ‘This is my place,'” said Dr. Hagelin.
Catch a flycatcher
The researchers attached the decoys to small trees or tied them to large sticks positioned vertically in soft soil. They hung beautiful mist nests and played flycatcher calls from speakers hidden in the bushes under the decoy. Scientists expect that if there is a real flycatcher in the area, it will fly into the wooden interloper and end up in their nets. Some birds do that, responding quickly to the lure. But sometimes it can take some time to catch a flycatcher. “Maybe two, if we’re lucky,” said Dr. Hagelin.
Attach a tag
The researchers used clear plastic cord – designed for making beaded jewelry – to thread tiny flycatcher harnesses, each with a geolocator tag. Once they have the bird in hand, they place the harness loops around its legs, positioning the tag on its lower back.
When the birds fly south for the winter, geolocator tags regularly record light levels and times, allowing scientists to estimate each bird’s approximate latitude and longitude. In the later years of the study, they switched to using GPS tags, which can provide more accurate location data.
Do it again a year later
To download the data, the researchers had to recapture the same birds the following summer. “Retrieving this information added to my gray hair,” said Dr. Hagelin. The second time, the birds were more cautious and less responsive to the deception of the scientists, so the researchers spent a lot of time watching the flycatcher nests.
“You can start to see patterns like the locations or directions that birds tend to exit or enter the nest and how they move through the trees,” said Dr. Hagelin. “So you can put a net on the road and hopefully catch them that way.”
Cross your fingers
Over the course of the five-year study, the researchers were able to deploy 95 tags. They recovered 17 geolocator tags but only five GPS tags — and three of the GPS tags failed, yielding no data for reasons scientists still don’t understand. “That was really devastating,” said Dr. Hagelin.
“But all is not lost,” he added. Geolocator data points out 13 important stopping points, from Washington to southern Peru, along with the three main wintering grounds in South America, researchers reported in 2021. Tagging technology has improved, so scientists with an appetite for catching flycatchers can now focus on collecting more detailed data on those locations. “Am I the one to do this?” Said Dr. Hagelin. “Maybe if I had the funds.”
