Brown Boobies Follow Passenger Ferry Near Ogasawara Islands to Capture Fish

Brown boobies have been observed following a passenger ferry near Japan’s Ogasawara Islands to capture fish driven to the surface by the vessel. Citizen scientist Ryota Hayashi recorded the behavior while traveling on the ferry that links the islands.

The birds followed the ferry on its outbound trips from Hahajima island, where their nesting colony is located, and flew out to meet it on inbound journeys.

Hayashi, who works in research and development for engineering consulting firm Nippon Koei, stated that the birds appeared to be targeting flying fish flushed from the water by the vessel. He added that under natural conditions brown boobies may also feed on other small schooling fish such as sardines and related species.

The Ogasawara Islands form a subtropical archipelago that is part of Tokyo and lies roughly 1,000 kilometers south of Shinjuku and Shibuya.

Hiroyuki Tanoi, who researches seabirds in Japan and runs a website on the subject, stated that in April, in the early breeding season, brown booby numbers are still low and the number of individuals using the ferry is limited. He said that in August, as chicks grow and more food is required, the number of brown boobies using the ferry increases.

Hayashi stated that at present it is not known how brown boobies detect vessel movements or how they learn that ferries can provide feeding opportunities.

He said the birds may learn ferry-following behavior from their parents or by observing and imitating more experienced individuals. A study of Peruvian boobies found that 20 percent of birds fitted with GPS trackers and video cameras followed a large fishing fleet. Hayashi’s paper forms part of a growing citizen science movement.