< The Long Trek Of The Bar-Tailed Godwit

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Heard on All Things Considered

October 22, 2008 - MELISSA BLOCK, host:

If you need any further proof that birds absolutely rule - and some of us don't need that proof, but if you do - look no further than the bar-tailed godwit. It turns out the bar-tailed godwit can fly nonstop for 7,200 miles, flying for as long as nine days without a rest from Alaska to New Zealand and Australia. That's what researchers led by biologist Robert Gill discovered after they fitted some godwits with satellite transmitters. And Robert Gill, your research is published today, and you call these extreme endurance flights across the Pacific. How extreme are they?

Mr. ROBERT GILL (Research Wildlife Biologist, Alaska Science Center): The godwits are expending energy and able to maintain this expenditure at higher rates and for longer periods than anything we've known previously about any vertebrate, man included.

BLOCK: And the previous record for uninterrupted flight was what?

Mr. GILL: Colleagues have tracked birds from New Zealand to the Yellow Sea in China, which is about 5,000 kilometers. And the flights we just documented doubled that.

BLOCK: And as you're tracking these birds in migration, how did you know that they weren't stopping?

Mr. GILL: That's a good question. Because the units from the bird tells us its position and how fast it's traveling over the surface of the ocean. So we can look at land relative to where that position was last reported and the speed at which it's traveling, and we can figure out could a bird have detoured to land, stopped, and then got back on the track that the satellite is showing us? And invariably, birds would have had to have flown at totally unrealistic speeds to have done that.

BLOCK: So you knew they had kept in flight the whole time.

Mr. GILL: Yes.

BLOCK: Was there a point as you were watching them that you realized, we're up to nine days now. This is a bird who has not stopped.

Mr. GILL: Oh, yeah. We started thinking about that a couple days into the flight, just trying to get your mind around something flapping its wings for day after day after day.

BLOCK: Well, these godwits are going without food or water for as long as nine days. How do they do that? How do they keep going?

Mr. GILL: They reside at a place with a phenomenal food resource, the Yukon Delta of Alaska, probably the richest in terms of the amount of food items - in this case, clams and small worms - than any place we know of on Earth. And they put on tremendous amounts of fat. They double their body mass before migration. So when they take off, about 50 to 55 percent of their body is pure fat. And that's the fuel that gets them from Alaska to New Zealand.

BLOCK: So they burn all of that while they're flying. And I guess when they land, they need a good meal.

Mr. GILL: They do, indeed. Colleagues have reported them touching down wobbly-legged, immediately sit down on their bellies and go to sleep for a few hours.

BLOCK: Dr. Gill, what do you think you learned about migration from this work you've done and this incredible performance from the bar-tailed godwit?

Mr. GILL: This particular flight has, I think, really opened our eyes - those of us that are interested in this long-distance migration - to the fact that these birds appear to know where they are, vis-a-vis where they want to go, any given moment of that flight. So, they can take detours to find favorable winds; they can take detours to get out of opposing winds. And they're finding the tip of New Zealand, which is, you know, after an 11,000-kilometer flight, that's a little blip out in that Pacific Ocean. But they know exactly where it is.

BLOCK: Well, Robert Gill, good to talk to you. Thanks so much.

Mr. GILL: My pleasure.

BLOCK: That's biologist Robert Gill, lead author of a study on the 7,200-mile nonstop migration of the bar-tailed godwit. I'm tired just thinking about it. It's published today in the journal "Proceedings of the Royal Society B."

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