Giant ocean no match for tiny bird

Robert Royse

Giant ocean no match for tiny bird

A songbird that easily fits in the palm of your hand still piles on enough fat each fall to fly nonstop over the ocean from Canada to the Caribbean islands. Some ornithologists have long suspected that the blackpoll warbler, common in North America’s subarctic evergreen forests, takes a direct route over the Atlantic Ocean to South America, where it spends the winter. But others were not so sure a bird so small—it weighs just 12 grams, slightly more than a U.S. half dollar—could make that journey. Instead, they suggested the bird traveled south over land, perhaps using the same route it takes when traveling north come spring. Two years ago, researchers got a chance to solve the mystery when dime-sized “geolocators”—devices that can simultaneously record daylight and time data, enabling researchers to track an animal’s approximate route—became available. Independently, in 2013, a U.S. team and a Canadian group each outfitted about 20 blackpolls with geolocator backpacks. A year later, the U.S. team recaught three of these birds, and the Canadians found two more. The researchers found that blackpolls do indeed fly between 2270 and 2770 kilometers over the ocean. The birds take 2 to 3 days to reach either Hispaniola or Puerto Rico, a stopping point en route to Venezuela and thereabouts, the two teams report online today in a joint paper in Biology Letters. That’s a remarkable feat for a bird the blackpoll’s weight, the researchers say. But an even smaller bird, the ruby-throated hummingbird, which is one-third the warbler’s size, could ultimately beat the warbler’s record, they add. But even the tiniest geolocators are too big for the hummingbird, so researchers have yet to track the hummingbird’s migration over the Gulf of Mexico.