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THEY'RE OFF!

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Tens of thousands of bar-tailed godwits, globe-spanning members of the sandpiper family, began leaving New Zealand this month on the first leg of their annual 18,000-mile journey to Alaska and back. And a group of Anchorage biologists and bird enthusiasts plan to track them every bit of the way.

Nine of the godwits have been surgically fitted with data transmitters, each about the size and weight of a single AA battery, which send signals to orbiting satellites that bounce them back to earth. Eventually the information reaches the Alaska Science Center, maintained by the U.S. Geological Survey in Anchorage, which shares it online.

Each godwit has an ID and mug photo posted on the USGS site, so computer users can track their progress through the Internet as the shorebirds wing their way to a northern staging area in Southeast Asia, approximately three-fifths of the way to Alaska.

On March 22, a female bar-tailed godwit named D-4 and a male named D-8 became the first of the tagged birds to touch down in China -- at a spot about 6,300 miles northwest of New Zealand.

The trip took them 7 1/2 days and they never stopped to rest, according to USGS biologist Lee Tibbitts, who's tracking the godwits as a project assistant. As of Thursday, five of the tagged birds had begun migrating north, and four still remained in New Zealand.

One of those yet to leave, a female godwit named D-5, appeared to be heading in the wrong direction, having relocated from North Island to South Island.

"So she's going the opposite direction," Tibbitts said. "We're kind of curious if she'll turn around."

Since the USGS Web site comes equipped with a "Google Earth" interface, citizen scientists can actually glimpse the precise rice paddy or tide pool bordering the Yellow Sea where some of the godwits are now taking a breather.

In about a month, they'll begin a 4,500-mile flight east -- the second leg of their journey -- to breeding grounds in Western Alaska, where the godwits summer along the Yukon-Kuskokwim Delta.

The research is all part of the international Pacific Shorebird Migration Project, which will try to identify global threats to shorebirds -- from climate change to habitat destruction to the spread of infectious disease.

This year the project is also tracking the migratory flights of 15 bar-tailed godwits that winter in Australia and breed in Siberia, as well as three other shorebird species -- the bristle-thighed curlew, the long-billed curlew and the Hudsonian godwit.

Bar-tailed godwits, in particular, deserve attention, since their numbers in Western Alaska have dropped sharply in the past 20 years -- from about 150,000 individuals in the early 1980s to 90,000 in 2007, according to USGS biologist Bob Gill, the shorebird project director.

But as recently as five years ago, scientists didn't know exactly how the godwits managed to get from Alaska to New Zealand in late summer. Thanks to the transmitters, they now have evidence that shows the godwits do so by flying nonstop in a grueling -- no eating, no drinking -- 7,200-mile journey straight down the middle of the Pacific Ocean. It's a trip that lasts eight to 10 days.

"What we have there is the longest documented nonstop flight by any bird that propels itself by flapping its wings -- by far," Gill said.

Unlike soaring birds, such as condors or albatrosses that ride thermals for long distances with their wings held still, godwits lose altitude when they fall into a glide, so they keep flapping at an average speed of about 35 mph, Gill said. Nor can they land in the ocean to feed or rest, as seabirds do, since they aren't designed to fish and don't float very well.

"They become like a sponge," he said.

Why don't they simply rest on islands as they migrate? One answer is simple, Gill said: "They don't have to."

Summering in the invertebrate-rich tide flats of the Yukon-Kuskokwim Delta, the bar-tailed godwits manage to double their weight by gorging themselves on worms and clams.

Weather patterns help their journey south as well. With storms out of the west consistently raking the North Pacific, godwits have learned to depart Alaska on the back-side of a low-pressure system, catching the counter-clockwise winds that catapult them south by southeast at speeds between 60-80 mph.

Around Hawaii, they catch the clockwise flow of the front side of a late-summer high-pressure system, which redirects them south by southwest toward New Zealand. By the time they arrive in the South Seas, they've consumed all their fat and some of their muscle as well, Gill said. They arrive looking like emaciated rock stars, weighing half of what they did to begin with.

There are probably some good reasons why they evolved that way, Gill said.

By avoiding the conventional shorebird flyways that parallel coastlines, they also avoid predators and infectious diseases that accompany continental wildlife populations. Instead of investing energy in maintaining an immune system, they're able to funnel those calories toward flying.

The more direct route south also makes the flight distance shorter to New Zealand, which, similar to Western Alaska, is an ideal home for shorebirds, with few predators and invertebrate-rich tidelands.

The return trip north to Alaska in spring -- more than 10,800 miles -- is longer and more circuitous due to the prevailing winds. The godwits first have to follow the southeast trades to the equator, then struggle through possible West Pacific cyclones on their way to the Yellow Sea.

It's there that biologists have observed a cluster of potential threats -- from bird harvesting to habitat destruction -- that may be endangering the bar-tailed godwit. They also worry about the threat that poultry farms there could pose in transmitting the deadly H5N1 strain of avian flu to migratory birds.

"We haven't detected any case of high-pathogenic avian influenza in North America yet by birds coming from any route," Gill said.

However, he said, less threatening forms of avian flu have been detected in bar-tailed godwits.

The shorebird project, funded partly by the David and Lucile Packard Foundation, will continue to monitor the health of migratory birds throughout the year.

Find George Bryson online at adn.com/contact/gbryson or call 257-4318.

Migratory birds coming back

The first migratory birds of the year returned to Upper Cook Inlet recently, according to a bird report issued last week by the Anchorage Audubon Society.

Three large gulls -- which may have been either glaucous-winged or herring -- were spotted March 24 above the pioneers' home adjacent to the Delaney Park Strip.

And a few days earlier, two adult trumpeter swans dropped down on Spring Creek near Kepler-Bradley Park just south of Palmer.

Several raptors that migrate shorter distances have been spotted as well. On March 19, a juvenile golden eagle was observed above Merrill Field. And on March 23, two short-eared owls were sighted in the Palmer Hay Flats.

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