Seabirds Take Bathroom Breaks Only While Flying todayheadline

Seabirds relieve themselves only on the wing. Researchers at the University of Tokyo strapped cameras to streaked shearwaters and discovered that the birds defecate exclusively while flying, typically every 4 to 10 minutes, releasing about 5% of their body mass per hour.

The discovery began by accident. “I was studying how seabirds run on sea surface to take off,” said lead author Leo Uesaka of the University of Tokyo. “While watching the video, I was surprised that they dropped feces very frequently. I thought it was funny at first, but it turned out to be more interesting and important for marine ecology.”

Streaked shearwaters (Calonectris leucomelas) spend most of their lives soaring above the Pacific Ocean. To study their movements, Uesaka and his colleagues outfitted 15 birds with eraser-sized, backward-facing cameras attached to their bellies. Over the course of the experiment, the team recorded nearly 200 defecation events. The footage revealed a clear pattern: the birds consistently avoided pooping while resting on the sea surface. Instead, they relieved themselves in midair, often just after takeoff.

In some cases, the birds even appeared to launch into flight solely to use the bathroom, taking off, defecating within a minute, and landing again on the water. This surprising behavior points to a strong aversion to fouling the sea surface.

“Streaked shearwaters have very long and narrow wings, good for gliding, not flapping,” Uesaka explained. “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 team speculates that the behavior may help the birds in several ways. By pooping in flight, the birds may reduce the chance of soiling their own feathers, avoid attracting predators, or simply find it easier to relieve themselves while airborne rather than floating.

The rhythm of excretion was strikingly regular. During daylight hours, the shearwaters defecated about every 4 to 10 minutes, adding up to an estimated 30 grams of feces per hour, roughly 5% of the bird’s body mass. Such a rapid cycle raises questions about the physiological and ecological drivers behind it. “We don’t know why they keep this excretion rhythm, but there must be a reason,” Uesaka said.

The ecological implications are vast. Seabird guano is well known for enriching soils and coastal waters with nitrogen and phosphorus, but much less is known about its role in the open ocean, where these birds spend most of their lives. With an estimated 424 million shearwaters and related species flying over the world’s seas, the cumulative effect of their aerial bathroom breaks could fertilize plankton and influence marine food webs across immense regions.

Large animals such as whales are already recognized for their role in nutrient redistribution, sometimes called the “whale pump.” Seabirds may represent a parallel process, dispersing nutrients through steady aerial deposition. Understanding the scale of this contribution could reshape scientists’ understanding of pelagic nutrient cycles.

Uesaka plans to expand the work using cameras and temperature sensors with longer battery life, combined with GPS, to map where seabirds release their droppings at sea. By pinpointing excretion hotspots, researchers hope to measure the true ecological footprint of seabird feces in the open ocean.

“Feces are important,” Uesaka said. “But people don’t really think about it.”

The study highlights how a seemingly trivial detail of animal behavior can reveal hidden links between species and ecosystems. What began as an amusing observation of seabird bathroom habits may ultimately shed light on nutrient cycling across the world’s oceans.

Current Biology, DOI: 10.1016/j.cub.2025.06.058