“We’re using a dual isotope approach: strontium and hydrogen,” Crowley said. “Strontium reflects geology and hydrogen reflects precipitation patterns. They’re highly complementary.”
Strontium is one of the most common elements found on Earth. But its isotopes vary greatly depending on the geology of the area. Likewise, the isotopes of hydrogen found in animals varies widely depending on how much rain or snow falls in a region. Geologists have created detailed maps of these isotopes.
Animals absorb the isotopes in the food chain. Just as human hair contains information about the person's health and diet, the isotopes in feathers give each bird a unique geographic signature.
Crowley used a similar technique last year to study Henst’s goshawks, an elusive bird of prey found in Madagascar.
“This is a map of strontium ratios in North America. And here are hydrogen values. So any bird with a different value of hydrogen or strontium than what we find here must have come from somewhere else,” she said.
The project demonstrates the value that UC places on research as part of its strategic direction, Next Lives Here.