Scientists who attach video cameras to animals are usually seeking a creature’s-eye view. When Leo Uesaka stuck tiny cameras to the bellies of seabirds called streaked shearwaters, he turned those cameras around. So maybe what he captured wasn’t surprising — but the amount of it was.

“The frequency of the excretion is far more than I expected,” Dr. Uesaka said.

A behavioral ecologist at the University of Tokyo, Dr. Uesaka had intended to study how the seabirds run along the water’s surface as they take off in flight. But when the No. 1 thing he noticed in his recordings was No. 2, he decided to shift his focus. He learned that streaked shearwaters almost never defecate in the water. Yet they go more than five times an hour, on average, while flying. The finding was published Monday in the journal Current Biology.

“You’d be surprised that a paper on bird poop could be that fascinating,” said Kyle Elliott, a behavioral ecologist at McGill University who was not involved in the study.

The findings might seem to confirm the worst fears of beachgoers who have been menaced by circling sea gulls. But the droppings of streaked shearwaters, which usually forage far out at sea, are unlikely to detonate on a sunbather’s towel. They might have effects, however, on the movement of nutrients through ocean ecosystems.

Streaked shearwaters are large birds that search for fish over the western Pacific. Dr. Uesaka and his colleagues study the birds at their breeding ground on a small, uninhabited Japanese island.

For the new study, Dr. Uesaka gathered nearly 36 hours of video footage of the birds on their daytime foraging trips, and watched all of it himself. “The backside is not very interesting,” he said. “So I’m always watching the time.”

As the minutes crawled by, he noticed that the birds were relieving themselves not just frequently, but regularly, each following a personal rhythm. Most of the 15 birds he recorded went every four to 10 minutes — more often than any other seabirds that have been studied.

By keeping some of the birds briefly in a cardboard box and collecting their guano, the researchers estimated that streaked shearwaters excrete 5 percent of their body mass every hour.

Curiously, though, the birds almost never did their business while resting on the water. The authors speculated that the birds might be trying to keep their back ends clean or avoid tipping off predators. Or maybe pushing out guano while floating is less comfortable for them.

Dr. Elliott said that it made sense for these birds to spend as little time on the water as they can. Like their relatives the albatrosses, shearwaters are efficient, wind-propelled fliers. Energetically, “It actually costs them less to fly than to rest on the water. So they really want to be flying,” he said. Sitting on the water might also make them lose body heat. For the streaked shearwaters, apparently, even a bathroom break isn’t worth a pit stop.

As meals from several hours ago travel through the birds’ digestive systems, Dr. Elliott said, the birds may simply be excreting as often as they’re able, to make their flight easier.

Dr. Elliott compared it with his experience flying in small planes in the Arctic. “When the load is too heavy, you have to leave it behind, right?” he said. “There’s a real cost to flying with a heavy load.”

All those loads of guano dropping into the ocean are more than just waste.

Seabird guano contains nitrogen and phosphorous that act as fertilizer wherever they fall. For example, coral grows twice as fast around islands with seabird populations than around neighboring islands with few seabirds. Populations of reef fishes are also greater around the seabird islands.

“The differences are incredible,” said Ruth Dunn, a marine ecologist at the research institute CNRS in France who was not involved in the study, but has used forward-facing cameras to watch red-footed boobies catch flying fish. If the streaked shearwaters tend to congregate over certain areas of the ocean, their fecal contributions could be affecting those ecosystems, too.

As Dr. Uesaka continues his investigation of seabird stools, he’s now attaching small GPS devices to his subjects along with the cameras. That will show him whether the birds are concentrating their excretion over a certain part of the ocean.

He also wants to repeat his research with other birds. But ultimately, Dr. Uesaka hopes that he has revealed a new way to use video loggers in research: The most forward-thinking investigation might be a rear view.