The amazing non

Researchers marvel at the godwits’ unusually long migratory flight that takes them from Alaska to New Zealand across the Pacific this time of year. No question of stopping to eat or rest along the way. How to explain such exploits?

The Pacific Ocean has long been considered an impassable barrier for most land birds. This perspective has since been upended by the documentation of astonishing migratory exploits. Due to the immensity of the Pacific and its climatic complexity, the study of these extreme birds provides a better understanding of fundamental migratory phenomena. In this regard, the case of the marbled godwit is particularly fascinating.

An epic journey

The Marbled Godwit is a species of shorebird in the Scolopacidae family. One of its two subspecies, Limosa fedoa beringiae, evolves in the Alaska Peninsula. During the September/October period, dozens of these birds take advantage of the favorable winds to begin their incredible annual migration from the mudflats of southern Alaska to the beaches of New Zealand and eastern Australia. These birds are looking for an endless summer, enjoying relatively safe and food-filled environments.

The barges perform this course of more than 11,000 kilometers across the Pacific flapping its wings night and day, without stopping to eat, drink or rest. This epic journey, the longest non-stop migration of a land bird in the world, can last about ten days.

The known distance record is currently 13,000 kilometers. It was established last year by an adult male who veered off course on its way to New Zealand to end up in Australia due to bad weather. This bird had flapped its wings for 237 hours without stopping. Last week, he left Alaska for the south again.

In March, the return distances are even longer, as the barges take a less direct route. The birds fly nonstop from New Zealand to China’s Yellow Sea and its rich mudflats, where they refuel and then return to Alaska. During these round trips of approximately 30,000 kilometers, the survival rate is over 90%.

New monitoring techniques now make it possible to see a little more clearly on those flights that were previously thought impossible.

A group of godwits in New Zealand. Credits: Peregrine

Birds built to last

Other birds stay aloft for long periods of time using a technique called “dynamic volleying”. Godwits continuously flap their wings, which takes more energy. However, these “ultra-endurance athletes” have evolved to allow this kind of epics.

Godwits are indeed so-called metamorphic birds, endowed with an unusual plasticity. A few days before the big departure, their internal organs undergo strategic restructuring. Their gizzards, kidneys, livers, and guts shrink to lighten the load, while their pectoral muscles grow to support the constant flapping of wings.

Shortly before departure, these birds also gorge themselves on insects, worms and other molluscs to double their weight and rely on fat to fuel their efforts. However, the energetics of their nonstop migration remain largely misunderstood. Current models show that these birds should collapse after three or four days.

Barges are also built for speed with streamlined wings and a missile-like body.

Whether the birds sleep or not is still debated. It has in fact been demonstrated that certain species of birds are capable of unihemispheric sleep (which only keeps half of their brain awake to fly). However, others believe godwits do not sleep at all and catch up on sleep once in New Zealand.

Finally, note that the lungs of these birds are among the most efficient of all vertebrates, allowing them to store enough air in the thin atmosphere of higher altitudes. In Russia, some barges have recently been documented flying at altitudes of five kilometers above the ground.

barges
A barge on a New Zealand beach. Credits: Malcolm Schuyl

Orientation and transmission

The question of their astonishing ability to orient still questions specialists. cross a Pacific Ocean almost without relief, and therefore without navigational landmarks, indeed requires some well-oiled techniques. Godwits probably rely on several cues, especially the sun and stars. Some experts believe they may be able to detect magnetic lines through a process called quantum entanglement.

Also remember that in general, birds also have a supernatural talent for weather forecasting. In fact, these animals can predict when to go and when not to go, or how high to fly.

Finally, the fact that young godwits make mistakes suggests that these are not purely instinctive behaviors. However, how migration abilities are passed on to the next generation is still unknown.

The amazing non-stop journey of barges across the Pacific