Researchers found that streaked shearwaters have strict bathroom schedules, pooping every four to 10 minutes and almost always while flying, not while floating. Credit: Yusuke Goto (CC BY-SA).
New research has detected the unusual excretion rhythm of some seabirds, showing that they only poop while flying over the ocean.
The research team indicates that there must be a reason why the streaked shearwater seabirds consistently excrete every 4 to 10 minutes, suggesting it may play an important role in fertilising the ocean.
“Faeces are important,” says Leo Uesaka, the lead author of the study from the University of Tokyo, Japan. “But people don’t really think about it.”
Seabird droppings are high in nitrogen and phosphorus making them great fertilisers for coastal waters as well as enriching the soil on land.
While previous researchers have studied what role these nutrients play in shaping the environment on land, there has been less research into how they impact the marine ecosystem.
Uesaka recorded almost 200 bird bathroom breaks using small, backward facing cameras which were strapped to the bellies of 15 streaked shearwaters, a common western Pacific species of seabird.
When analysing the videos, Useaka found that the birds almost always relieved themselves while flying, especially shortly after take-off. The researchers estimate that the birds excreted 30 grams of faecal matter every hour, which is about 5% of their body mass.
On a couple of occasions when the birds were floating along the water, Uesaka noticed the birds would take off, excrete, and then return to their floating position within a minute. This suggests that the birds intentionally avoid excretion while floating.
“Streaked shearwaters have very long and narrow wings, good for gliding, not flapping,” says Uesaka.
“They have to flap their wings vigorously to take off, which exhausts them. This means the risk of excreting on the sea surface outweighs the effort to take off. There must be a strong reason behind that.”
The researchers suspect this habit may help the birds avoid attracting predators or keep their feathers free from faeces. They also suggest flying could simply help the birds defecate more easily than in the floating position.
However, the team didn’t initially intend on researching streaked shearwater droppings.
“I was studying how seabirds run on the sea surface to take off,” says Uesaka.
“While watching the video, I was surprised that they dropped faeces very frequently. I thought it was funny at first, but it turned out to be more interesting and important for marine ecology.”
Uesaka plans to continue the research by using a GPS and cameras or temperature sensors with longer battery life to better understand how and why the seabirds choose where to excrete.
“We don’t know why they keep this excretion rhythm, but there must be a reason,” says Uesaka.
The results have been published in Current Biology.