Kuaka bar-tailed godwits make the longest non-stop flights, and researchers are using hi-tech tags to solve the mystery of how and when they sleep.

Godwits hold the record for non-stop long-distance flight - and scientists are wondering when they find time to sleep on the wing.

The long-distance godwit migration

Eastern bar-tailed godwits or kuaka spend up to six months every year in Australasia. At last count, in 2020, the total summer population was estimated at 126,000 birds - 78,000 birds were in New Zealand and the rest in eastern Australia.

After spending the summer feeding on rich intertidal mudflats in the southern hemisphere, the godwits fly north in March. They follow a route known as the East Asian-Australasian Flyway, which takes them to Alaska, via the Yellow Sea. From New Zealand they take seven or eight days to cover the 10,000-or-so kilometres to reach large areas of tidal mudflats in China, Taiwan and Korea. They feed here for four to six weeks, before moving on to the Alaskan tundra, where they breed.

In October they return south, and it is these journeys that have catapulted the godwits into the record books.

Long-haul champions

Godwits make the longest non-stop migration of any bird. We only discovered this when satellite trackers got small enough to be used on them.

In 2007, a female known as E7, set the first record: 11,680 kilometres non-stop. With no breaks for food or rest, she flew for more than eight days, over the open Pacific Ocean, from Alaska to New Zealand.

E7's epic migration has since been eclipsed by the 13,560 kilometre non-stop journey made by bird B6 in 2022. B6 was tagged as a juvenile in Alaska and was just 5 months old when it made its first-ever 11-day flight to Tasmania. Scientists do not know how these young birds find their way to New Zealand and Australia on that first flight - they fly in flocks, and perhaps these flocks include an adult guide?

Sleep in birds

If you've ever taken a long-haul flight from New Zealand you've probably experienced sleep deprivation. Now imagine you're a small bird, flapping your wings continuously, unable to land or feed, on a flight that will take anywhere from 8 to 11 days. When and how do you sleep?

How godwits sleep during their epic flights is the focus of a new research project involving 45 godwits from the Motueka sandspit.

This sleep project involves ornithologist Jesse Conklin, from the United States, and Bart Kempenaers, Mihai Valcu and avian sleep expert Niels Rattenborg, all from the Max Planck Institute for Biological Intelligence, in Germany. …

Go to this episode on rnz.co.nz for more details