PARIS - A diminutive songbird weighing the equivalent of just three teaspoons of sugar can fly over the north Atlantic, scientists said on Tuesday, resolving a 50-year mystery.
The tiny superbird is the blackpoll warbler (Setophaga striata), they reported in the journal Biology Letters.
Tipping the scale at a mere 12 grammes (4.2 ounces), the white-throated, black-capped bird migrates each autumn from New England to South America.
For half a century, scientists have debated whether the birds fly non-stop over the ocean or take breaks on land to carry out this marathon flight.
Backpack flight recorders, attached to 40 of the birds, have now provided "irrefutable evidence" that they do it all in one go, the scientists said.
The geolocators, weighing only 0.5g (0.02 ounces), found that the birds completed an astonishing non-stop flight of between 2,270 and 2,770 kilometres (1,410-1,721 miles).
This was the distance from their summer homes in Vermont and Nova Scotia to Puerto Rico, Cuba and the Greater Antilles islands, where they made landfall before continuing to northern Venezuela and Colombia.
The devices were able to track the birds' flight path but were not big enough to transmit the data in real time.
Three devices with the stored information were recovered for analysis from the Vermont birds, and two from the Novia Scotia group.
Albatrosses, sandpipers and gulls are famous for their ultra-long flights - but they have broad, long wings and can settle on water if they get tired or blown off course.
For a forest bird no bigger than a tennis ball, which would drown if it touched the sea, to do such a feat is a wonder, the researchers said.
"For small songbirds, we are only just now beginning to understand the migratory routes that connect temperate breeding grounds to tropical wintering areas," said Bill DeLuca at the University of Massachusetts Amherst.
"We're really excited to report that this is one of the longest non-stop overwater flights ever recorded for a songbird, and finally confirms what has long been believed to be one of the most extraordinary migratory feats on the planet." The trackers provided confirmation that had thwarted previous investigations into the blackpolls.
"The indirect evidence in favour of an Atlantic voyage was fairly strong," said Ryan Norris, a professor of biology at the University of Guelph, Ontario.
"You have birds landing on ships in the Atlantic, radar studies off the tip of Nova Scotia showing the birds heading south, and very few sightings of blackpolls in the southern US in the fall."