Seabirds Expel 5% of Their Entire Body Mass Hourly During Flight Over the Sea

In a groundbreaking study published in the prestigious journal Current Biology, a team of researchers led by Kyle Elliott, a behavioral ecologist at McGill University, have shed light on an unexpected aspect of seabird behaviour – their excretion habits.

The focus of the study was the streaked shearwater, a bird species known for its elegant flights over the Pacific Ocean. Over a period of 36 hours from 2021 to 2023, the researchers fitted tiny belly-mounted cameras onto these birds to observe their movements and habits.

The findings were astonishing. Streaked shearwaters were found to drop 195 loads of feces, with almost all of them splattering into the Pacific Ocean from mid-air. Each bird pooped every 4-10 minutes, equating to more than five times an hour. Some birds even took off from the water just to relieve themselves, landing moments later.

The study revealed a "precise periodicity" in the birds' pooping, but the cause remains a mystery – whether it's a digestive quirk or an evolved strategy. Understanding the frequency of defecation at sea is important for understanding the spread of diseases among flocks of streaked shearwaters.

Moreover, the excretion of seabirds, including that of streaked shearwaters, is packed with nitrogen and phosphorus. Seabird guano is crucial for understanding nutrient cycles in the ocean. The study suggests that seabirds, such as shearwaters, are aerial nutrient couriers, offloading packages that ripple through marine food webs. In the open ocean, the cumulative effect of seabird excretion could rival the "whale pump".

Interestingly, some streaked shearwaters were observed to drop feces on their companions, potentially accelerating the spread of viruses such as bird flu between flocks. Pooping in flight may help the birds avoid pathogens like avian influenza and avoid attracting predators such as sharks and seals.

The study of seabird excretion has revealed that some of the Pacific's most elegant fliers are also some of its most relentless fertilizer machines. Biologist Joe Roman suggests that all species, including seabirds, play a role in the movement of nutrients between systems.

The researchers who collaborated with Leo Uesaka on the study of Streaked Shearwaters include Masaki Tsuda, Hiroyuki Watanuki, and Seiji Yamamoto. The findings about seabird excretion were first published in a study by Kyle Elliott and his team, offering a fascinating insight into the secret circulatory system of ecosystems. The ocean's health depends not just on what animals eat, but on what they expel.