In 2022, a young bar-tailed godwit made the most extraordinary journey. These birds are known for their long migrations, but this individual, named B6, set an avian world record when it flew non-stop from Alaska to Tasmania. That's an epic journey of 8,425 miles in 11 days. Researchers have studied how these exceptional birds can complete such an impressive journey.
Bar-tailed godwits (Limosa lapponica) are fairly large wading shorebirds. Their length is between 13 inches and 16 inches, with a wingspan of around 29 inches.
They are mainly a mottled brown color, but are lighter underneath. One of their most noticeable features is their long bill, which they use when they forage for food. Their diet varies with the season and location, but when they are on soft, coastal substrates, they probe to the full depth of their bill to retrieve mollusks, crustaceans, and worms. When they are on their breeding grounds, they feed on insects, spiders, and berriesamong vegetation.
Twice every year, millions of birds make an epic journey along a migration superhighway. It's called the East Asian-Australasian Flyway, and it's like a freeway for birds. Among them are two bar-tailed godwit subspecies. One of them isLimosa lapponica baueri,which breeds in western Alaska but migrates to New Zealand and southeast Australia for the non-breeding season. The entire flyway bar-tailed godwit population is around 325,000, of which 155,000 areLimosa lapponica baueri.
A study using satellite telemetry followed the bird's migration journey in 2007. Some birds were fitted with small transmitters so that scientists could track their route. Starting in their non-breeding grounds in Australia/New Zealand, they begin their northward migration but typically complete it in two stages. The first half of their journey follows the west Pacific Rim to the Yellow Sea, which lies between mainland China and the Korean peninsula. This stage is around 6200 miles, takes between six and eight days, and is completed in a single flight. The birds then remain in the North Yellow Sea area for several weeks before completing the second stage of the flight to theirAlaskan breeding grounds. Here, they stay for most of June, July, and August before leaving in late August to return south. Their return journey crosses the Pacific Ocean and is non-stop.
Their incredible non-stop Pacific journey is aided by strong tailwinds, so the birds can average speeds of around 34 mph. Ever since scientists started studying this journey, records have been broken! It started in 2007 when a female named E7 completed her 7257-mile journey in just over 8 days. Her record was smashed by a male called 4BBRW in 2020. This bird flew over 7456 miles from Alaska to New Zealand in 11 days, but it would only hold the record for two years.
In 2022,a team of scientists from the U.S. Geological Survey, the Max Planck Institute, and the U.S. Fish and Wildlife Service tracked some juvenile bar-tailed godwits from breeding sites near Nome, Alaska. These young birds were undertaking their very first migration. This was a staggeringly challenging journey for such young birds.
One particular bird, called B6, was four or five months old when it left the Kuskokwim Delta, Alaska, on October 13th. It was carrying a 5-gram solar-powered satellite transmitter. As a result, scientists were able to confirm that it finally touched down on October 25th inTasmania. It had travelled 8,425 milesand had flown non-stop for 11 days and 1 hour, or 265 continuous hours!
Birds cannot undertake such extreme journeys without careful preparation. Bar-tailed godwits feed for most of August, building up fat reserves. By the time they leave, their fat reserves make up over half of their body weight. This will sustain them during their flight. Because they don't feed during their journey, their gizzard and intestines are not needed and therefore shrink to almost nothing. The birds also do not drink and use the water produced when their bodies burn fat for hydration. These birds are active flyers; they do not glide, so this bird was flapping its wings the entire time.
Exactly how these birds know the route for such a long journey is still largely unknown. Most of the Alaska breeding population of bar-tailed godwits head forNew Zealand, and the rest find their way to the east coast of mainland Australia. Normally, the adults set off first, leaving the chicks behind to fatten up a little more. Most juveniles meet up with the adults along the way, and as a group, the birds figure out how to get to their destination.
For B6, however, the journey did not go to plan. It either lost its way or was buffeted by winds (or both), and it eventually ended up on Tasmania. However, this is not the end of the bird's adventures. Over the course of its lifespan, the average bar-tailed godwit travels more than 300,000 miles!