Many of us want to retreat to warmer sanctuaries at the first signs of winter, but what are you willing to do to get there? If a layover in Miami sounds arduous, consider the blackpoll warbler (Setophaga striata): When the temperature drops, it heads south from the northeastern U.S. for the warmth of the Caribbean, a journey of nearly 3,000 km. Unlike you, however, the blackpoll warbler makes the journey under its own power – and without stopping.
“This is one of the most audacious migrations of any bird on earth,” said Chris Rimmer, an ornithologist at the Vermont Center for Ecostudies and co-author of a new paper on the warbler flights. “We’ve also documented one of the longest nonstop, overwater flights ever recorded for a songbird.”
Weighing a scant 12 grams, the warbler makes the second-longest nonstop flight of any bird, and easily the longest when accounting for its size. While other birds – seagulls and albatrosses, for example – are known for making cross-ocean flights, the warbler is a tree-dwelling bird and lacks the luxury of water landings.
To track the warblers, researchers outfitted them with tiny geolocators, resembling tiny bird backpacks. They then tracked the birds, who departed in early fall. In as little as two days, the birds made it from the northeast over the Atlantic to either Hispaniola or Puerto Rico. After a rest, they continued on over the Caribbean to their winter nesting grounds in South America. It’s odd for a land-based bird to choose an oceanic flight path, but the scientists figure that the warblers have decided that the benefits of a direct path over water outweigh the risks.
Of course, the warblers use some physical tricks to make the nonstop flights possible. Though their normal weight is only about 12 grams, the birds will bulk up by about 1/3 before departing, weighing in at about 16 grams. The extra fuel is important, as it determines how far they can fly. Relatively unnecessary bodily processes are also shutdown as they prepare for the journey.
“It does fatten up, by almost doubling body weight and absorbing many of its digestive organs. It turns into a lean, mean flying machine, just wings, fuel and a small orientation computer,” says William DeLuca from the University of Massachusetts in Amherst.