Bar-tailed godwit goes the
By Ned Rozell
October 10, 2007
On the evening of Oct. 7, 2007, a female bar-tailed godwit leapt
off a mud flat at the mouth of the Kuskokwim River. The bird
might not touch the ground again until it reaches New Zealand,
more than 7,000 miles away.
Bob Gill, a biologist with the U.S. Geological Survey in Anchorage,
saw on his computer that the bird had taken flight on its fall
migration from Alaska to New Zealand. A few weeks earlier, Gill
and his colleagues had tracked another female godwit on a flight
to New Zealand. They found that the bird remained in the air
for eight straight days.
On Aug. 29, that bird, called E7 for a tag on its upper leg,
took off from the Yukon River Delta. Biologists tracked it as
it flew to North Cape, New Zealand and landed on Sept. 7. Gill
knows the bird didn't land on the journey because of its constant
movement as he and others tracked it.
U.S. Geological Survey
Biologist Bob Gill believes bar-tailed godwits have the ability
to sense upcoming storm systems that give them tailwinds for
much of their long journeys across the globe.
Photo by Phil Battley.
Biologists in New Zealand captured
E7 in February and implanted a transmitter in its abdomen. That
satellite transmitter showed that the godwit left New Zealand
in mid-March and flew nonstop to China, a continuous flight of
6,300 miles that took eight days. The bird remained there for
five weeks before taking off for its breeding grounds in Alaska.
On May 2, the godwit left China and headed out over the Sea of
Japan and the North Pacific, taking six days to reach the Yukon-Kuskokwim
Delta. This flight, also nonstop, covered 4,500 miles. The bird
summered in Alaska; where it fattened up on marine worms and
thumbnail-size clams that it plucked from the mud with its long
After a summer of breeding and feeding on Alaska's riches, the
godwit known as E7 began a 7,200-mile nonstop flight to New Zealand,
the equivalent of a flight from San Francisco to New York, and
then back to San Francisco again. Only the Concorde-shaped godwit
never stopped to refuel. And pausing on the ocean wouldn't do
a godwit much good anyway - adapted to life on the shore, the
birds can't feed on the water, or swim for a long time.
Gill thinks the birds have somehow evolved to be avian meteorologists,
with the ability to sense upcoming storm systems that give them
tailwinds for much of the journey (E7 cooked out of Alaska at
60 mph, but sometimes slowed to 35 mph in areas with low winds).
Gill and other researchers also have noted that the birds' bodies
start changing in anticipation of the great storms that help
"They shrink their digestive machinery-their gizzards and
intestines get smaller-prior to flight," Gill said.
During E7's flight from Alaska, the bird headed for Hawaii, then
turned southwest toward Fiji before heading south to New Zealand.
Along the way, flying at altitudes as high as 15,000 feet, the
bird lost 50 percent of its body weight, and may have shut off
half its brain to nap along the way, an ability researchers have
noted in mallard ducks.
The flight path of
a bar-tailed godwit that flew direct from Alaska to New Zealand.
Courtesy USGS Science Center.
How E7 and other godwits find their way from Alaska to the tip
of New Zealand is a mystery to scientists. Birds will often zigzag
down, following weather patterns, but "once they're into
the Tropics, it's mostly straight to New Zealand," Gill
Not all bar-tailed godwits make the nonstop flight. A few tagged
birds have run into headwinds in the second half of their journey
and have touched down before reaching their destination, Gill
If the battery on its transmitter survives, the godwit that left
the Kuskokwim on Oct. 7 may allow scientists to find that it
also will keep beating its wings over the sea until it reaches
New Zealand around Oct. 15, when it will finish a silent, incredible
"I've been studying them 20 years and it's still jaw-dropping
to me," Gill said.
This column is provided
as a public service by the Geophysical
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University of Alaska Fairbanks, in cooperation with the UAF
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