Going the Distance

A marathon is 26.2 miles long, the approximate distance from Marathon, Greece, to Athens.  The race gets its name from the Battle of Marathon, fought over 2,500 years ago; legend has it that when the Athenians defeated the Persians, they sent a squire named Pheidippides to share the good news with those gathered in the capital.  Pheipiddies ran the distance without stopping, delivered his message (“We have won!”) and collapsed on the spot, dead from exhaustion.

The bar-tailed godwit knows no such fate.

Pictured above, the bar-tailed godwits are a type of migratory bird.  They weigh, on average, about a pound, give or take half a pound, and eat and rest only on land.  The birds are native to Australia but breed in the Northern Hemisphere — primarily in Alaska, Scandinavia, and northern Asia.  But note that the trip from Australia to Alaska is, almost entirely, over the Pacific Ocean, without any land of which to speak.  This fact highlights a peculiarity of the bar-tailed godwit: it can travel extreme distances — thousand of miles at a time — without stopping for food, rest, or even sleep.

In February of 2007, researchers in New Zealand, working with the United States Geological Service’s (USGS) Alaska Science Center, captured 16 bar-tailed godwits and outfitted them with satellite tags. The birds were set free, now able to be tracked by the USGS scientists.  One of the birds, named “E7” (due to its tracking code), was tracked migrating up to Alaska via China. The first leg of the flight, according to the BBC, was a record 6,340 mile trek. The second leg was a similarly impressive 3,000 mile trans-Pacific flight to Alaska.  But E7 wasn’t done yet.  On her return-trip to New Zealand, she skipped the China stop-over, and, as denoted by the red line on the right, below, went direct — an eight-day trip of approximately 7,250 miles.  That’s two and a half times the distance of New York to Los Angeles or nearly four times the distance between Paris and Moscow.

How do these birds do it? While much of it is a mystery to us, NPR has a few details.  First, the birds eat an enormous amount before taking flight, doubling their body weight as some internal organs which will not be very useful during the trip (such as intestines) shrink to make room for the extra fat.  All of this additional weight is lost during the trip.  Second, the bird kind of, sort of sleeps on its journey — again, as NPR states, by “shutting down one side of the brain at a time.”

In total, the typical bar-tailed godwit will fly 300,000 migratory miles over its roughly 20 year lifespan.

Bonus fact: Birds which migrate in a V formation do so for two reasons, per Scientific American: one, to make it easier for the flock to stick together, as the last birds can see the others; and two, to decrease air resistance, making the flight easier.  In the latter case, each bird flies a bit higher in the sky than the one ahead of it, allowing it to travel while expending less energy.

From the Archives: Marathon Madness: The crazy story of the 1904 Olympic marathon.

Related: “Amazing Birds: A Treasury of Facts and Trivia about the Avian World” by Roger Lederer.  Five stars on six reviews.