Every autumn, the blackpoll warbler (Setophaga striata) flies south from Canada or New England. And it doesn’t stop until it lands, three days later, on the northern coast of South America, a new study finds. That’s a distance of up to 2,770 kilometers (or 1,721 miles). By any stretch, that’s quite a feat for a bird that weighs a mere 12 grams — or just a little more than two U.S. quarters.
Radar and other evidence had pointed to impressive southern migrations by these birds. But a study now provides “the first irrefutable evidence” that they make it nonstop.
It “confirms what has long been believed to be one of the most extraordinary migratory feats on the planet,” report a team of U.S. and Canadian researchers. On April 1 in Biology Letters, they describe the birds’ amazing over-water trek.
Scientists put devices on some blackpolls in late spring and summer. These lightweight instruments measured daylight. It allowed the researchers to establish sunrise and sunset times at the birds’ locations. Those times differ with latitude — or how far north or south some place is from the equator. So these devices established generally where the birds were on any given day.
Those light-measurement devices showed that all but one of the monitored birds took off for their southern treks between September 25 and October 21. What’s more, the birds took out over the Atlantic. With no place to land, the birds just forged on until they reached their destinations.
Those mini-fliers kept up a brisk pace. They averaged 38 to 48 kilometers per hour (24 to 30 miles per hour) the whole time. The scientists used computers to calculate the birds’ calorie intake and how many of those calories would have been used to fuel their migrations. The birds’ bodies indeed could physically make the journey, those calculations showed.
Especially interesting: The new study showed the birds do not retrace the route they fly each spring. When traveling north, these warblers fly over land. And along the way they stop for periodic breaks. So the big question that remains: Why do these small fliers take such a dangerous over-water route when going south?
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Atlantic One of the world’s five oceans, it is second in size only to the Pacific. It separates Europe and Africa to the east from North and South America to the west.
calorie The amount of energy needed to raise the temperature of 1 gram of water by 1 °C. It is typically used as a measurement of the energy contained in some defined amount of food.
latitude The distance from the equator measured in degrees (up to 90).
migration (v: to migrate) Movement from one region or habitat to another, especially regularly and according to the seasons.