In Montana, as in most of the Lower 48, American Robins are present year-round. So I had long assumed that the cheerful songbird hopping around my yard in the fall had nested nearby that summer. Imagine my surprise, then, to learn it may have spent those months a thousand miles or more to the north. Where these common birds go, and what drives their decision to migrate long or short distances—or simply stay put—are mysteries that scientists are just starting to solve.
“They’re a truly cosmopolitan bird,” says Emily Williams. “They may be the most widespread songbird in North America, and yet there’s so much we don’t know about them.”
The research could also have implications for human health. In a 2015 study in California, researchers reported that robins, as well as other common birds, are reservoirs for Lyme disease—a bacterial infection transmitted to humans by tick bites, largely in the Northeast, mid-Atlantic, and upper Midwest regions. It’s well known that mice and deer spread the disease to ticks in new areas. The discovery that robins carry infected ticks, too, raises concerns that they’ll accelerate Lyme’s spread, says Alex Jahn, an Indiana State evolutionary ecologist who leads the robin project. “Because they’re migratory, a robin could potentially carry this bacteria and infect ticks across counties, across states, across the continent,” he says, “dispersing it much more effectively than a deer could.”
The team checks each robin they capture for ticks and send any they find for testing. Ultimately, Jahn aims to combine new insights about robins with the Lyme disease findings, along with information about weather, climate, and land transformation, to develop a forecasting system that could detect disease outbreaks and other threats.