Birds are famous for airborne speed and endurance. Some have been clocked flying 60 miles per hour or more. Others make annual migrations from Alaska to New Zealand, nonstop.

But for scientists, tracking birds as they perform those feats has been an intractable problem. Now researchers think they have cracked it with a novel device — a tiny bird backpack that contains sophisticated sensors and weighs less than a dime.

The new technology has opened up vast new possibilities for bird researchers. Already, it is yielding surprising findings — for example, that some birds fly even faster than previously thought. But its real importance, biologists say, is the opportunity to unlock mysteries of bird migration that could help preserve species threatened by habitat loss and climate change.

“We knew that purple martins went to Brazil and wood thrush went to Central America,” said Bridget J. M. Stutchbury, a biologist at York University in Toronto, who with colleagues fitted birds from the species with the sensors and mapped their migrations last year. “But the details of how an individual gets there, what routes they take, how fast they fly, how often they stop to rest — these are the kinds of details we have never been able to have.”