Streaked Shearwaters Prefer to Excret in Air, New Study Shows

Ornithologists of the University of Tokyo have observed excretions of striated shearwaters (Calonier Leucomelas) In the open ocean using video cameras mounted on the belly. These sea birds have shown a tendency to avoid excretions while floating on the surface of the sea and excreted regularly during the flight; Excretion schedules have shown a periodicity, occurring every 4 to 10 minutes during clarity hours with inter-event intervals varying in a few minutes.

The striated shearwater (Calonier Leucomelas), a kind of sea bird found in the peaceful ocean. Image credit: Kanachoro.

Understanding when and how much sea birds excreen at sea is important to understand their potential influence on marine ecosystems.

The whales are known to redistribute nutrients by excretion, the “whale pump”.

The large and widespread populations of sea birds could also shape the processes of key pelagic ecosystems.

“I studied how sea birds operate on the surface of the sea to take off,” said Dr. Leo Uesaka, a researcher at the University of Tokyo.

“Watching the video, I was surprised that they dropped the excrement very frequently.”

“I thought it was funny at first, but it turned out to be more interesting and important for marine ecology.”

Using cameras back and backwards attached to the belly of 15 striated shearwaters, Dr. Uesaka and his colleague, Dr. Katsufumi Sato, recorded and analyzed nearly 200 defecation events.

They found that the birds almost always dinned by stealing and that defecation often followed shortly after takeoff.

Sometimes the birds took off only for bathroom breaks and returned to water in one minute.

These results suggest that they intentionally avoid poop in floating.

“Striped shearwaters have very long and narrow wings, good for slipping, not beating,” said Dr. Uesaka.

“They have to beat their wings vigorously to take off, which exhausts them.”

“This means that the risk of excreting on the surface of the sea prevails over the effort to take off. There must be a strong reason behind this. ”

Researchers suspect that this habit can prevent birds from increasing feathers with excrement, helping them avoid attracting predators or helping birds more easily compared to a floating position.

In flight, the birds pooped about 4 to 10 minutes.

The authors estimated that the birds excrete 30 grams of poop every hour, or about 5% of their body mass.

“We do not know why they keep this rhythm of excretion, but there must be a reason,” said Dr. Uesaka.

To find out, scientists plan to use cameras or temperature sensors with a longer battery life, combined with a GPS, to map where sea birds release their excrement at sea.

They hope that these future studies will offer additional information on the role of sea birds excrement in marine ecology.

“The excrement is important. But people don’t really think about it,” said Dr. Uesaka.

The results appear today in the newspaper Current biology.

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Leo Uesaka & Katsufumi Sato. Periodic excretion models of sea birds in flight. Current biology 35 (16): R795-R796; DOI: 10.1016 / J.Cub.2025.06.058