A ‘fish finder’ for birds? Route-dependent foraging behavior of the brown booby ( Sula leucogaster ) following a passenger ferry in the Ogasawara Islands, Japan

Brown boobies (Sula leucogaster) exhibit route-dependent foraging behavior around passenger ferries, suggesting that these vessels may act as 'fish finders' by disturbing surface-associated prey like flying fish. Research conducted in the Ogasawara Islands, Japan—home to one of the largest breeding colonies—revealed a directional asymmetry: significantly higher numbers of boobies accompanied ferries departing from the main colony island (Hahajima) compared to southbound trips. The behavior peaked during the chick-rearing period in August, with birds following the ferry immediately upon departure but only appearing mid-route when traveling toward the colony. This pattern hints at cognitive abilities such as spatial memory and associative learning. The study highlights the potential of low-cost observational methods from public transport for behavioral research, offering a scalable approach for citizen science.

Hayashi, R. (2026). A ‘fish finder’ for birds? Route-dependent foraging behavior of the brown booby ( Sula leucogaster ) following a passenger ferry in the Ogasawara Islands, Japan. PeerJ, 14, e21093. Portico. https://doi.org/10.7717/peerj.21093