Adhesive seed dispersal by birds has gotten less attention in previous studies. However, seabirds are possibly effective dispersers by adhesion in isolated islands where plant introductions occur less frequently and seabirds breed in dense colonies. Our previous studies showed seed adhesion to seabirds and relation between ranges of attached plant species and seabird colonies in the Ogasawara Islands. Current study was aimed to clarify how the seeds attach to seabird bodies.

We focused on brown boobies which are major breeding species in the Ogasawara Islands. They are considered to be effective dispersers because seed adhesions to them were observed at some frequency, and unlike petrels, they often rest on lands other than their colonies. However, walking is less common for them. Thus, we examined the possibility that seeds attached via nest materials.

The analysis of nest materials showed that they often used plants with seeds for their nests. Such seeds can attach to their bodies easily. Plants whose seeds had been confirmed to adhere to the boobies (e.g. Boerhavia diffusa, Solanum nigrum and Chloris barbata) were also found in nests. Preference for nest material of the disperser should determine the dispersed plant species, and plant seeds that could not easily attach in usual situation can be effectively dispersed.