Every autumn, the bar-tailed godwit embarks on one of the most extraordinary journeys in the animal kingdom. This small bird, no larger than a chocolate bar, flies more than 13,000 kilometers across the Pacific Ocean without landing, stopping, or even sipping water. Starting from Alaska and ending in Tasmania or New Zealand, the journey spans a vast, open ocean with no islands or refueling points. In 2022, a young godwit named B6 set a new record, flying 13,560 kilometers in just 11 days and one hour—equivalent to two and a half trips between London and New York, or about a third of Earth’s circumference. To accomplish this incredible feat, the bar-tailed godwit undergoes a dramatic transformation before its flight. In the weeks leading up to departure, the bird gorges on mollusks, crustaceans, and marine worms, building up fat reserves that will fuel its entire journey. This fat can make up more than half of the bird’s body weight, turning it into a living fuel tank. Unlike humans, who might struggle with such a long journey without rest or food, the bar-tailed godwit is perfectly adapted to this extreme challenge. What is even more remarkable is the bird’s ability to shrink and reorganize its internal organs to accommodate the massive fat reserves. The digestive system, which would be unnecessary during the flight, atrophies, while the powerful pectoral muscles that drive the wings grow stronger. This internal restructuring is guided by hormonal changes and occurs naturally, without any external assistance. Scientists first discovered this phenomenon in 1998 when they observed that the intestines, livers, and kidneys of departing birds were significantly smaller than those of birds that had not yet begun their journey. Modern tracking technology has allowed researchers to document these incredible flights in detail. A satellite transmitter attached to B6’s back recorded its 13,560-kilometer journey, providing an hour-by-hour account of its non-stop flight. This technology, which is now more advanced than the early models used in 2007, has revealed not only the physical endurance of the bird but also its remarkable navigational abilities. Unlike other seabirds, the bar-tailed godwit cannot swim, meaning any navigational error could result in a fatal fall into the ocean. Yet, it remains awake and active for nearly two weeks, crossing vast, unbroken waters with unwavering precision.