A new study published in the journal Current Biology has revealed a peculiar bathroom habit of seabirds; they always poop while flying rather than floating on water, doing so every 4 to 10 minutes.
The research, led by the scientists at the University of Tokyo, used small video cameras and attached them to the bellies of 15 streaked shearwaters (Calonectris leucomelas) breeding at Japan’s Funakoshi Ohshima Island.
Reviewing the footage, the team analysed over 195 defecation events and found the birds overwhelmingly preferred flights to relieve themselves.
“The footage captured far more frequent defecation events than I had expected. The fact that we were able to study this behaviour at all was a surprise in itself,” the lead author, Leo Uesaka, told Discover Wildlife.
Using backward-facing cameras mounted on streaked shearwaters, researchers recorded seabirds’ pooping habits in the open ocean Credit: Leo Uesaka
The analysis showed that almost all excretions happened while in the air, and half of those take-offs witnessed defecation within 30 seconds. Some birds took off, pooped, and returned to the water within a minute, suggesting these flights solely served discharging.
Surprisingly, the excretion was also very frequent. Based on calculations using the defecation rate per hour and faecal mass, the team estimated that the streaked shearwaters typically excreted 5% of their body mass (typically 400-600g).
Uesaka says that even the stored food in the stomach increases the energy needed for flight. Shedding weight by excretion could make a meaningful difference to flight efficiency. Considering the energy required to take off from water, this behaviour implies that the benefits of frequent pooping exceed the flight cost.
Scientists offer some plausible explanations for this behaviour. Excreting in flight keeps feces away from feathers, reducing the chances of pathogenic infection. It may also lower the chances of attracting potential predators such as sharks and seals that may respond to faecal odour and plumes.
The findings from the study are relevant to the wider ocean, too, say the authors, who explain that the droppings may contribute to transporting nutrients over vast distances, similar to the ‘whale pump’ – the ecological process where the feeding and excretion habits of whales help circulate nutrients in the ocean.
Seabird faeces have high nitrogen and phosphorus contents, which may supply nutrients to plankton in the water below. While the faecal disposal of a single bird may seem minimal, an estimate of over 424 million individuals may have a significant cumulative impact.
“Faeces are important,” Uesaka says. “But people don’t really think about it.”
Top image: streaked shearwaters in Japan. Credit: Leo Uesaka
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