It takes guts to migrate long distances – literally, if you’re a bar-tailed godwit Limosa lapponica baueri. This crow-sized shorebird burns not just flab, but even some innards to fuel its marathon migrations.
Each autumn, the godwit flies from its breeding grounds in Alaska and Siberia to Australia or New Zealand to spend the winter. The bird may travel for nine or ten days, covering a mind-boggling 11,000km, without pausing to rest or eat.
It’s the longest journey without a pit stop of any animal on Earth.
To prepare, it crams itself full of fuel by feeding ravenously until it is morbidly obese.
The godwit preys on mussels, clams and other not-so-lean cuisine in the weeks before the trip. But the feast doesn’t end at the seashore. In a process called autophagy, the bird consumes a large portion of its internal organs. Up to a quarter of certain vitals, including its kidneys, liver, gizzard and intestine, is broken down.
This process creates space for more fat – an efficient and long-lasting fuel – and makes the bird lighter and thus more efficient on the wing. By departure day, the godwit is like a ball of bacon: up to 55 per cent lard.
Shrinking its insides also saves the energy that would otherwise be consumed in maintaining body parts useless for the trip.
Yet the heart and flight muscles retain their mass, rendered more powerful serving a lighter body.
Hence, the godwit may look like it’s all flab and feathers, but it’s built to go the distance.
The facts of fat
By shrinking their organs, the birds shed about half of their non-fat weight before migrating.
Once the godwit is at its winter destination, it regrows its internal organs in their entirety, making the bird one of the world’s biggest losers, and gainers, of tissue.
This article by David Butvill was first published by Discover Wildlife on 15 October 2025. Lead Image: Credit: Diana Robinson Photography/Getty Images.
What you can do
Help to protect wildlife by donating as little as $5 – it only takes a minute!
Our conservation partners spend at least 90 percent of the money raised on actual fieldwork rather than administration and fundraising.
Supertrooper
Source link