As the sun was setting over the Firth of Thames in New Zealand, dozens of bar-tailed godwits shuffled about lazily on the edge of the bay, the wind fluffing their feathers.
The tide was coming in, submerging the mudflats where the birds had been feeding, sticking their long bills into the soft earth to dig up worms and crabs. As the water advanced, they stopped foraging and waded ashore, inelegantly carrying their plump, butterball bodies on stilt-like legs. A bit homely and ungainly, with drab plumage, godwits appear quite ordinary. As the sky turned orange, they settled down to roost. Resting for hours on end, they can seem rather sedentary.
Nothing could be further from the truth. Six months earlier, these birds had made an epic journey to get here, flying all the way from Alaska. Astonishingly, they didn’t stop along the way. For eight or nine days straight, they flew, beating their wings the entire way: about 7,000 miles, more than a quarter of the way around the world.
When the godwits arrived, they were bedraggled and emaciated. They had fattened up now for their migration back to Alaska, where they breed during the summer. They were going to fly about 6,000 miles, to the Yellow Sea. There they would spend about six weeks along a coastline split between China, North Korea, and South Korea, feeding and resting before flying 4,000 more miles.
Bar-tailed godwits have made this migration for thousands of years, but a clear picture of their travels has emerged only in the past few decades. Although migrations by birds have been a source of wonder for centuries, new scientific findings are helping to demystify them while adding to our appreciation of these incredible feats. At the same time, scientists are discovering how human activity and climate change are disrupting and possibly imperiling these ancient journeys.
The disappearance of godwits from New Zealand during the months when they breed led the Maori to view godwits—which they call kuaka—as birds of mystery. The sentiment is reflected in a Maori saying about the unobtainable: “Who has ever held the egg of the kuaka?” By the 1970s bird-watchers and biologists suspected the godwits in New Zealand were the same ones that nested in Alaska. But it was only in 2007 that scientists were able to determine the migration routes.
Researchers Bob Gill and Lee Tibbitts, wildlife biologists with the U.S. Geological Survey, were part of a team that captured a small number of godwits and implanted satellite transmitters inside an air sac in their abdomens, leaving the antennas sticking out. Between March and May, they tracked a group on their northern migration. The batteries of the transmitters weren’t expected to last beyond the summer, and sure enough, one by one, they stopped working. Except one. On August 30, 2007, a godwit known as E7 departed from Alaska, still transmitting its position.
With a rising sense of excitement, the researchers followed the bird’s progress as it flew past Hawaii, past Fiji, and then, on September 7, past the northwestern tip of New Zealand. “It was a nail-biter because the battery was failing,” recalls Tibbitts. That night E7 landed in the Firth of Thames. At eight days and eight nights, and 7,150 miles, it’s still the longest nonstop migratory flight ever recorded. “It is a head-scratching, jaw-dropping feat,” says Gill, now an emeritus scientist with USGS.
The tracking of E7 served to deepen the curiosity that bird migrations have long inspired. Where do they go? How can they fly as far as they do? How are they able to find their way to the same winter and summer sites year after year? Advances in satellite tracking and other technologies are enabling researchers to explore those questions in unprecedented detail. (...)
Like other long-haul migrants, godwits prepare by building enormous reserves of fat in the weeks leading up to their departure. The equivalent of gasoline, fat is what fuels the birds. When the godwits leave, more than half their body weight is fat. They look like feathered croquet balls, with a layer of fat under the skin up to an inch thick and more fat encasing their abdominal organs. “I call them lard asses,” says Phil Battley, an ornithologist at Massey University in New Zealand.
As they fatten up, their pectoral and leg muscles also grow larger. Other long-distance migrants, such as red knots, shrink the gizzard and other organs in preparation for flight—the equivalent of jettisoning excess cargo.
Godwits, like other migratory species, don’t rely just on their own power; they also take advantage of winds. The birds tend to depart from Alaska on the tail end of storms that produce winds blowing south. Their departure from New Zealand also coincides with favorable conditions for traveling. “You get pretty benign winds when you leave New Zealand,” Gill says, “but then they are able to hook into others as they go north.” When they leave the Yellow Sea for Alaska, the winds once again have shifted to be with the birds.
Researchers assume that godwits, which are not known to soar, flap their wings for most of their journey, even when riding winds, while other species, such as albatrosses, do soar.
Some species possess an astonishing flexibility in regulating their sleep. Niels Rattenborg at the Max Planck Institute and his colleagues went to the Galápagos Islands to study the sleeping habits of great frigatebirds, which have seven-foot wingspans and fly hundreds of miles over the Pacific Ocean looking for food. The researchers, capturing frigatebirds in their nests, implanted sensors to track brain electrical activity and glued data-recording devices on their heads before releasing them. Besides keeping track of location and altitude, the devices helped the researchers determine sleep patterns.
After spending up to 10 days over the Pacific, the frigatebirds returned to their nests and Rattenborg’s group retrieved the devices. The data showed that the birds slept in short bursts lasting an average of 12 seconds, usually while soaring, that added up to an average of 42 minutes a day. That was a mere fraction of the 12 hours a day the birds slept when they were in their nests. For a substantial part of the time that they napped in the air, the birds only put half of their brain to sleep, while keeping the other half awake.
To learn whether godwits rely on similar sleep patterns in flight, researchers need considerably smaller batteries—a goal Rattenborg says is within reach. “It’s possible that they get some sleep on the wing, perhaps even while flapping,” he says.
by Yudhijit Bhattacharjee, National Geographic | Read more:
Image: Jonathan Harrod, Minden Pictures
The tide was coming in, submerging the mudflats where the birds had been feeding, sticking their long bills into the soft earth to dig up worms and crabs. As the water advanced, they stopped foraging and waded ashore, inelegantly carrying their plump, butterball bodies on stilt-like legs. A bit homely and ungainly, with drab plumage, godwits appear quite ordinary. As the sky turned orange, they settled down to roost. Resting for hours on end, they can seem rather sedentary.
Nothing could be further from the truth. Six months earlier, these birds had made an epic journey to get here, flying all the way from Alaska. Astonishingly, they didn’t stop along the way. For eight or nine days straight, they flew, beating their wings the entire way: about 7,000 miles, more than a quarter of the way around the world.When the godwits arrived, they were bedraggled and emaciated. They had fattened up now for their migration back to Alaska, where they breed during the summer. They were going to fly about 6,000 miles, to the Yellow Sea. There they would spend about six weeks along a coastline split between China, North Korea, and South Korea, feeding and resting before flying 4,000 more miles.
Bar-tailed godwits have made this migration for thousands of years, but a clear picture of their travels has emerged only in the past few decades. Although migrations by birds have been a source of wonder for centuries, new scientific findings are helping to demystify them while adding to our appreciation of these incredible feats. At the same time, scientists are discovering how human activity and climate change are disrupting and possibly imperiling these ancient journeys.
The disappearance of godwits from New Zealand during the months when they breed led the Maori to view godwits—which they call kuaka—as birds of mystery. The sentiment is reflected in a Maori saying about the unobtainable: “Who has ever held the egg of the kuaka?” By the 1970s bird-watchers and biologists suspected the godwits in New Zealand were the same ones that nested in Alaska. But it was only in 2007 that scientists were able to determine the migration routes.
Researchers Bob Gill and Lee Tibbitts, wildlife biologists with the U.S. Geological Survey, were part of a team that captured a small number of godwits and implanted satellite transmitters inside an air sac in their abdomens, leaving the antennas sticking out. Between March and May, they tracked a group on their northern migration. The batteries of the transmitters weren’t expected to last beyond the summer, and sure enough, one by one, they stopped working. Except one. On August 30, 2007, a godwit known as E7 departed from Alaska, still transmitting its position.
With a rising sense of excitement, the researchers followed the bird’s progress as it flew past Hawaii, past Fiji, and then, on September 7, past the northwestern tip of New Zealand. “It was a nail-biter because the battery was failing,” recalls Tibbitts. That night E7 landed in the Firth of Thames. At eight days and eight nights, and 7,150 miles, it’s still the longest nonstop migratory flight ever recorded. “It is a head-scratching, jaw-dropping feat,” says Gill, now an emeritus scientist with USGS.
The tracking of E7 served to deepen the curiosity that bird migrations have long inspired. Where do they go? How can they fly as far as they do? How are they able to find their way to the same winter and summer sites year after year? Advances in satellite tracking and other technologies are enabling researchers to explore those questions in unprecedented detail. (...)
Like other long-haul migrants, godwits prepare by building enormous reserves of fat in the weeks leading up to their departure. The equivalent of gasoline, fat is what fuels the birds. When the godwits leave, more than half their body weight is fat. They look like feathered croquet balls, with a layer of fat under the skin up to an inch thick and more fat encasing their abdominal organs. “I call them lard asses,” says Phil Battley, an ornithologist at Massey University in New Zealand.
As they fatten up, their pectoral and leg muscles also grow larger. Other long-distance migrants, such as red knots, shrink the gizzard and other organs in preparation for flight—the equivalent of jettisoning excess cargo.
Godwits, like other migratory species, don’t rely just on their own power; they also take advantage of winds. The birds tend to depart from Alaska on the tail end of storms that produce winds blowing south. Their departure from New Zealand also coincides with favorable conditions for traveling. “You get pretty benign winds when you leave New Zealand,” Gill says, “but then they are able to hook into others as they go north.” When they leave the Yellow Sea for Alaska, the winds once again have shifted to be with the birds.
Researchers assume that godwits, which are not known to soar, flap their wings for most of their journey, even when riding winds, while other species, such as albatrosses, do soar.
Some species possess an astonishing flexibility in regulating their sleep. Niels Rattenborg at the Max Planck Institute and his colleagues went to the Galápagos Islands to study the sleeping habits of great frigatebirds, which have seven-foot wingspans and fly hundreds of miles over the Pacific Ocean looking for food. The researchers, capturing frigatebirds in their nests, implanted sensors to track brain electrical activity and glued data-recording devices on their heads before releasing them. Besides keeping track of location and altitude, the devices helped the researchers determine sleep patterns.
After spending up to 10 days over the Pacific, the frigatebirds returned to their nests and Rattenborg’s group retrieved the devices. The data showed that the birds slept in short bursts lasting an average of 12 seconds, usually while soaring, that added up to an average of 42 minutes a day. That was a mere fraction of the 12 hours a day the birds slept when they were in their nests. For a substantial part of the time that they napped in the air, the birds only put half of their brain to sleep, while keeping the other half awake.
To learn whether godwits rely on similar sleep patterns in flight, researchers need considerably smaller batteries—a goal Rattenborg says is within reach. “It’s possible that they get some sleep on the wing, perhaps even while flapping,” he says.
by Yudhijit Bhattacharjee, National Geographic | Read more:
Image: Jonathan Harrod, Minden Pictures
