Eurasian reed warblers captured during migration and then dumped 620 miles off course were able to find their way back to their original route, according to a study suggesting some birds can truly navigate.
This means that the birds could identify at least two coordinates roughly corresponding to geographic latitude and longitude and suggests they are not limited to north-south direction as some had thought, the researchers said on Thursday.
"This finding is surprising and presents a new intellectual challenge to bird migration researchers, namely which cues enable birds to determine their east-west position?" Nikita Chernetsov at the Zoological Institute in Russia wrote in the journal Current Biology.
The researchers found that after dropping the warblers off 620 miles east, the birds somehow corrected their direction by shifting their orientation to get back on the correct path home.
Other studies have suggested that birds use the position of the sun or geomagnetic information to determine latitude, which defines north or south location, the researchers said.
The Russian team said migrating birds such as the warblers might rely on two internal clocks, one to set their "home time" and the other to their wintering grounds. Geomagnetic information might also play a role, they said.
"We have experimentally shown beyond reasonable doubt that long-distance, intercontinental avian migrants can correct for east-west displacements during their return migration in spring," Chernetsov wrote. "This means that they can determine geographic longitude, even though we do not currently know how they do it."