London – A small songbird no bigger than a sparrow flies 1,700 miles over open ocean in a non-stop flight in what has been described as one of the “most extraordinary migratory feats on the planet”, a study has found.
Scientists said that the annual open-water flight of the tiny blackpoll warbler from the north-east corner of North America to the forests of South America is one of the greatest migratory journeys.
It was thought that the songbird, which spends summer in the boreal forests of Canada and the United States before heading south for the winter, flies overland down the eastern coast of America, stopping on its way to rest and feed.
However, a study involving miniature electronic backpacks to monitor the birds' movements has revealed that the blackpoll warbler simply flies due south over open water in a “fly-or-die” journey without stopping until it reaches landfall in the Caribbean about two or three days later, before flying on to Venezuela and Colombia.
“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,” said Bill DeLuca of the University of Massachusetts Amherst, the first author of the study published in the journal Biology Letters.
Seabirds such as the Arctic tern and albatross are known to migrate many hundreds of miles over open sea but it is unusual for such a small songbird, which weighs only 12 grams and normally lives in woodlands, to fly for such a long time over the ocean, Dr DeLuca said.
The warbler is too small to carry conventional tracking devices so it was fitted with a small, lightweight recorder to monitor the time of sunrise and sunset, which allowed the scientists to estimate its precise longitude and latitude over a given time period.
The scientists fitted the recording backpacks to 20 warblers before they flew south for the winter and managed to retrieve the devices from five individuals during the following season,
“When we accessed the locators, we saw the blackpolls’ journey was indeed directly over the Atlantic. The distances travelled ranged from 2,270km to 2,770km” said DeLuca.
“It was pretty thrilling to get the return birds back, because their migratory feat in itself is on the brink of impossibility. We worried that stacking one more tiny card against their success might result in them being unable to complete the migration,” Dr DeLuca said.
“They eat as much as possible, in some cases doubling their body mass in fat, so they can fly without needing food or water,” said Ryan Norris of the University of Guelph, the team leader.
The scientists suggested that the birds use the quicker, oversea route rather than the longer, coastal path because there are fewer overall risks in making a shorter journey compared to a longer trip over land.
The Independent