Bar-tailed Godwit

The bar-tailed godwit holds the confirmed record for the longest non-stop flight of any bird. Satellite tags have tracked individuals of the subspecies that breeds in Alaska flying directly south across the open Pacific Ocean to New Zealand and eastern Australia, a route with no land to stop on, covering distances of more than 13,000 kilometres in a single continuous flight lasting roughly 11 days. One tracked juvenile bird was recorded flying over 13,500 kilometres in about 11 days on its first-ever migration, without any adult guidance, food, fresh water, or rest on solid ground.

The bar-tailed godwit prepares by undergoing dramatic physiological changes before departure. It gorges on food at its staging grounds until fat makes up around half of its body weight, providing the fuel for the flight, and at the same time its digestive organs, including the stomach, intestines, and liver, shrink substantially because they will not be used in the air and would only add dead weight, while its flight muscles and heart enlarge. During the flight it burns through this enormous fat store, arriving emaciated, and then rapidly regrows its digestive system so it can begin feeding again, a cycle it repeats each migration.

It cannot sleep in the way a resting bird does, because it must remain in continuous, controlled flight for the entire multi-day ocean crossing, with no possibility of landing on the water as a seabird could. It is thought to manage by taking extremely brief periods of rest, possibly allowing one half of the brain to enter a light sleep state at a time while the other half stays alert enough to maintain flight, a strategy documented in some other birds, along with very short micro-sleeps, so that it accumulates small amounts of rest without ever fully losing control of flight.

The single greatest threat is the loss of the intertidal mudflats it relies on as refuelling stops, particularly on its northbound spring migration. Large numbers of godwits stage on tidal flats around the Yellow Sea, between China and the Korean Peninsula, to feed intensively and rebuild fat reserves before continuing to the Arctic, and extensive reclamation of these mudflats for ports, industry, and agriculture over recent decades has destroyed a large fraction of this critical habitat. Because the godwit's migration strategy depends on a small number of very specific, high-quality stopover sites, the loss of even a few of them can affect the whole flyway population, which is reflected in the species' Near Threatened status.