Warblers that weigh about as much as a stack of 12 business cards fly thousands of miles across the Atlantic during their fall migration.
Imagine a journey that requires you to first pack on the pounds, then get rid of your intestines, and finally to forgo eating and sleeping for three days. For the blackpoll warbler, such a feat is called their fall migration.
Barely half an ounce (12 grams), these tiny birds fly from northeastern Canada to South America every fall. But no one knew what path they took. It turns out the warblers fly nonstop over the Atlantic Ocean, researchers report March 31 in the journal Biology Letters.
Ecologists affixed lightweight tracking devices to five blackpoll warblers during the fall 2013 migration to discover the animals’ overwater route.
The warblers fuel up on fat for the journey, going from 0.4 ounces (12 grams) to 0.6 ounces (16 grams), says lead study author Bill Deluca
, an ecologist at the University of Massachusetts, Amherst. Some overachievers double in weight. “Basically, they’re these little meatballs with wings,” he says.
Then they absorb internal organs they won’t need for the trip, like their intestines, to reduce excess weight, Deluca says. Reduced to fat, feathers, and muscle, the birds depart, taking advantage of trade winds for their journey south.
The warblers can’t catch these winds on their way back, so they take an overland route in the spring, Deluca explains.source : http://news.nationalgeographic.com/2015/03/150331-blackpoll-warbler-bird-migration-atlantic-animals-science/