05/06/2026
Godwits are an amazing bird found at certain times of the year around the Whau estuary. Do you know when we will see them next in NZ?
In September 2007, a female bar-tailed godwit known to scientists as E7 lifted off from the mudflats of western Alaska and began flying south. She did not stop to rest, she did not look for fresh water, and she did not descend to feed. Seven days and nine nights later, she touched down on the shores of New Zealand. She had traveled roughly 7,145 miles over the open expanse of the Pacific Ocean in a single, unbroken journey.
Biologists with the U.S. Geological Survey had long suspected that Alaska-breeding godwits performed an eleven-thousand-kilometer direct Pacific crossing each autumn. The mathematics of bird migration pointed to it, and the seasonal arrivals and departures aligned perfectly. But proving that a shorebird could cross the largest ocean on Earth without a single break required real-time tracking. E7 provided the definitive, individual proof that transformed a grand scientific hypothesis into an undeniable reality.
A bar-tailed godwit is not a large bird. Weighing barely a pound, it possesses long legs and a slender, upturned bill designed for probing mud for marine worms and mollusks. It is a shorebird, built for wading, not a seabird like an albatross that can rest on the ocean surface or soar effortlessly on thermal currents. If a godwit touches the water, it will drown. To survive a trans-Pacific crossing, E7 had to stay airborne for over two hundred consecutive hours.
To prepare for a journey of this scale, the godwit undergoes a radical physical transformation in the weeks leading up to departure. E7 spent the late Alaskan summer feeding continuously, swelling her body with thick layers of subcutaneous fat until she nearly doubled her normal weight. This fat was her fuel, but carrying that much weight required structural trade-offs.
Before takeoff, a godwit's internal architecture shifts. The bird's digestive organs, including the stomach, intestines, and liver, actively shrink and atrophy, reducing unnecessary weight and conserving energy. Meanwhile, the heart and flight muscles enlarge to handle the extreme, prolonged workload. By the time E7 took flight from the Yukon-Kuskokwim Delta, she was essentially a streamlined pair of wings attached to a massive fuel tank, operating with only the bare essential organs required to keep her in the air.
E7 carried a tiny, 9.5-gram satellite transmitter surgically implanted by researchers earlier that year. The transmitter pinged her location to orbiting satellites, allowing scientists on the ground to watch her progress across an empty ocean landscape.
The route was entirely unforgiving. Once a godwit leaves the coast of Alaska, there are no landmarks, no places to seek shelter from storms, and no food supplies. E7 flew through a shifting mosaic of weather systems, navigating by a combination of the Earth's magnetic fields, the position of the sun and stars, and a highly sophisticated internal sense of weather patterns.
Godwits do not just endure the wind; they select their departure times to ride massive atmospheric currents. E7 utilized favorable tailwinds from favorable weather systems to push her south, maximizing her speed while minimizing the rate at which she burned through her fat reserves. Even with the wind at her back, the physical toll was immense. As the days blurred together over the open ocean, her flight muscles continuously burned through her fat stores. When the fat was completely depleted, her body began to systematically break down and consume its own muscle tissue for energy.
On the eighth day of her journey, the tracking data showed E7 approaching the northern coast of New Zealand. She finally glided down toward the mudflats of the Firth of Thames, a critical shorebird habitat on the North Island.
When she touched the ground, she was a skeletal version of the bird that had left Alaska a week prior. She had lost more than half her body weight, her digestive tract was shut down, and her flight muscles were severely degraded. Yet, within hours of landing, her internal organs began to regenerate, allowing her to process food again and begin rebuilding the mass she had burned across the Pacific.
E7's flight remains a definitive milestone in the study of avian migration. Her journey showed that the bar-tailed godwit does not view the Pacific Ocean as a barrier, but as a highway. She was never an elite anomaly among her species; she was simply the first one carrying the technology to show us what these shorebirds have been doing quietly, every autumn, for thousands of years.
Source: U.S. Geological Survey (USGS) Migratory Bird Research Reports, 2007 / Gill, R. E. et al. (2009). Proceedings of the Royal Society B: Biological Sciences.
