A recent study from Japan has highlighted the significant role Streaked Shearwaters play in enhancing marine ecosystems through their unique nutrient-cycling behavior. These seabirds frequently excrete nutrient-rich guano while in flight, effectively acting as aerial fertilizers for the ocean below.
Researchers attached cameras to 15 Streaked Shearwaters on Funakoshi Ohshima Island, observing that they defecate approximately every four to ten minutes during flight. This airborne habit is thought to be a strategy for maintaining hygiene or avoiding predators while resting on the water. The guano, rich in nitrogen and phosphorus, significantly boosts plankton growth, which in turn supports marine food webs, especially in nutrient-limited oceanic regions.
The ecological importance of seabird guano has long been recognized, historically used as a valuable fertilizer, in gunpowder production, and even for skin care. The Inca civilization valued guano so highly that they strictly controlled access to it, punishing disturbance of the birds with death. Understanding the integral role these birds play in marine ecosystems is crucial for their conservation. A rare observation of a Streaked Shearwater near Delaware Bay in May 2025 highlights the species' migratory paths and its conservation importance. This observation is the first documented case in the North Atlantic. Streaked Shearwaters undertake extensive migratory journeys, traveling from breeding grounds in East Asia to wintering areas in the seas around New Guinea, the Arafura Sea, and the South China Sea, distributing nutrients across vast oceanic distances, covering distances up to 5,400 km.
Globally, an estimated 840 million seabirds contribute to nutrient cycles, releasing approximately 591,000 tons of nitrogen and 99,000 tons of phosphorus annually. This input is vital for marine life, from plankton to coral reefs. Seabird guano can also play a role in restoring coral reefs after bleaching periods. The readily bioavailable nitrogen and phosphorus in guano are particularly effective in supporting marine ecosystems. However, Streaked Shearwater populations are facing gradual declines due to threats such as introduced predators on breeding islands and potential by-catch in fisheries, underscoring the importance of their conservation to maintain the ecological benefits they provide.
In the 19th century, the guano trade led to the "Era of Guano" and stimulated the colonization of remote bird islands.