OCEAN · FIELD GUIDE
The Sooty Shearwater — A Figure-Eight Across the Whole Pacific
Each summer, dark swirling flocks of seabirds astonish visitors off the California coast. For half the year they vanish. When scientists finally put tags small enough on them, the tracks drew something no one had seen before: a giant figure-eight stretched across the entire Pacific Ocean.
The birds that vanish
Every summer, millions of sooty shearwaters arrive off the coast of California — dark swirling clouds over the water that visitors sometimes mistake for smoke. For the other half of the year they disappear. Where they went was a mystery until tracking tags became small enough to follow a bird the size of a small gull.
A figure-eight across an ocean
A sooty shearwater — known to Maori as titi, or the muttonbird — left its breeding burrow on an island off southern New Zealand carrying a miniature archival tag. It flew north right across the equator into the northern hemisphere's summer, then settled for weeks in one of three rich feeding regions — off Japan, off Alaska, or off California.
As the northern autumn closed in, it turned south again, funnelling home through a narrow corridor in the central Pacific to complete a giant figure-eight that spanned the entire ocean. Along the way it covered as much as 900 km in a single day, feeding from the surface down to nearly 70 m.
A record drawn by a tiny tag
The whole loop measured about 64,037 km over roughly 262 days — at the time, the longest animal migration ever recorded electronically, later beaten only by the Arctic tern. The entire journey was logged by a tag weighing just a few grams, finally revealing where these familiar birds go for half the year.
One connected ocean
The shearwater's track is one of the most striking shapes in all of animal tracking: a figure-eight stretched across the whole Pacific. It revealed that a small, abundant, easily overlooked seabird integrates the resources of an entire ocean basin every year, chasing summer between the hemispheres — and it remains the clearest proof that the open ocean is one connected system in the eyes of the animals that cross it.
See it on the map
Switch on the Animal Journeys layer on the Ocean canvas to trace its figure-eight. The chevrons show its direction; the solid line is the full loop its tag recorded. It joins Nicole the great white, Adelita the loggerhead, the record humpback, E7 the godwit, Phyllis the elephant seal, the record leatherback and the record Arctic tern — each one real and drawn from published, citable science.
Source: Shaffer, S. A., Tremblay, Y., Weimerskirch, H., Scott, D., Thompson, D. R., Sagar, P. M., Moller, H., Taylor, G. A., Foley, D. G., Block, B. A., & Costa, D. P., "Migratory shearwaters integrate oceanic resources across the Pacific Ocean in an endless summer," Proceedings of the National Academy of Sciences 103(34):12799–12802 (2006).
Frequently asked questions
How far does a sooty shearwater migrate?
Tagged sooty shearwaters from New Zealand were tracked travelling 64,037 km round trip across the Pacific in about 262 days — at the time, the longest animal migration ever recorded electronically. They fly the entire length of the ocean in a figure-eight pattern (Shaffer et al., PNAS, 2006).
What is the figure-eight route?
From a breeding colony in southern New Zealand, the bird flies north across the equator into the northern hemisphere's summer, then settles for weeks in one of three rich feeding regions — off Japan, off Alaska, or off California. As the northern autumn closes in, it funnels home through a narrow corridor in the central Pacific, completing a giant figure-eight that spans the whole ocean.
What is a sooty shearwater?
The sooty shearwater (Ardenna grisea) is a soot-brown seabird about the size of a small gull, and one of the most abundant seabirds on Earth. In New Zealand it is known to Maori as titi, or the muttonbird. It feeds by plunging from the surface, reaching depths of nearly 70 m, and spends most of its life far out at sea.
Why does it cross the whole Pacific?
By migrating between the hemispheres, the sooty shearwater chases summer from one end of the Pacific to the other, living in near-perpetual daylight and near-perpetual plenty. It feeds in the most productive waters of both the Southern and Northern Hemispheres in a single year, integrating the resources of an entire ocean basin.
Why was this migration such a landmark?
When it was published in 2006, the 64,037 km figure-eight was the longest animal migration ever recorded with an electronic tracking device — later beaten only by the Arctic tern. It was made possible by miniature archival tags light enough to fit a small seabird, and it revealed that a familiar, overlooked bird quietly travels the length of the world's largest ocean every year.
Is the track on the map exactly the route it flew?
It is an honest schematic of the recorded route, not a claim of exact daily positions. The line follows the published figure-eight — north from New Zealand to a stopover off Japan, Alaska or California, then home through the central Pacific — drawn as a smooth loop. Every distance and figure shown is sourced (Shaffer et al., 2006).
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