White Pelicans have bred on Dassen Island since 1956; the island is one of only two breeding colonies in South Africa (the other being St Lucia). Most white pelican breeding occurs on Boom Point in the northwest on the island. The size of the pelican colony has increased steadily. The pelicans fly to the mainland to feed, but have taken to also eating the chicks of Kelp Gulls, Cape Cormorants & Swift Terns.
Until 1995, Leach's Storm Petrel was regarded exclusively as a nonbreeding migrant from the northern hemisphere. In 1971 it was found breeding on Dyer Island and in 1972 on Dassen Island too.