Five songbirds tagged with geolocators have migrated from the St. Croix River Valley to habitats as far south as Central America — and back.
Satellite images show the distant journeys of the wood thrush, a close relative to the American robin. Information taken from tiny backpacks attached to the birds last summer show the first wood thrush recaptured this summer in Minnesota had wintered in Mexico. Data was corrupted on a second bird, but it was confirmed that a third went to Honduras, another to Guatemala and another to Nicaragua.
"We just wanted to demonstrate where a single bird went," Chris Stein, superintendent of the St. Croix National Scenic Riverway, said Friday. "Now we have five. These readings help determine where the bird is on the face of the planet within 10 meters."
The wood thrush, known for its flutelike song and cinnamon-colored cape, needs large blocks of intact forest for protection. The songbird's population has dropped sharply since 1966, Stein said, because of lost habitat.
The two most recent arrivals were documented Thursday by Calandra Stanley, a University of Maryland researcher working in Minnesota this month. Stein had arranged the project with the Smithsonian Migratory Bird Center in hopes of learning from satellite readings where the species travels and what can be learned from its habitats.
"It's an important piece of the puzzle to try to solve the mystery of why the wood thrush is declining," Stanley said.
Last summer, tiny backpacks were affixed to 25 male songbirds with hopes of recapturing at least five. Each backpack, or tag, weighed just a bit more than a dime.
With five birds already recaptured, Stanley hopes to find one or two more in the final week of study. Four of the birds were found at Warner Nature Center north of Stillwater. The fifth was caught at Spring Lake Regional Park near Hastings.
Birds were lured into nets with recorded sounds of another bird singing, and all were recaptured within 200 meters — little more than the length of two football fields — of where they were tagged, Stanley said.
The bird that flew to Guatemala, recaptured Thursday, had spent the winter sheltered in shade coffee — coffee plants grown under a canopy of trees — or cocoa trees, Stanley said. Another bird captured Thursday appeared to have wintered in a mostly agricultural area, although poor-quality Google Earth imagery didn't allow detailed information about the habitat.
Tracking where the wood thrush migrates in winter will help in negotiations with Latin American countries to improve the fortunes of the small songbirds, Stein said.
"People can see we're all connected in this one world," he said. "Birds are a very important part of our environment here. We realize that if we want our birds to keep coming back here, our Neotropical migratory birds, we better protect their habitat as well."
Stein said he became interested in how birds in Minnesota and Wisconsin migrate to Latin America after the St. Croix Riverway, a national park, started a sister relationship with the Costa Rica national park service in 2013. That agreement is intended to study Neotropical migratory birds such as warblers, hummingbirds, orioles and tanagers that nest in the St. Croix Valley.
He doesn't expect to find wood thrushes migrating to Costa Rica, although any findings about particular species contribute to overall understandings of bird migratory patterns, he said.
The wood thrush project is a joint effort by the riverway, the Warner center and Carpenter Nature Center. The $15,000 needed to pay for the project came from the St. Croix Valley's Riverway Endowment Fund, Stein said.