Effects of habitat modification on breeding seabirds: A case study in Central Chile

Many seabird nesting arcas have been altered by human activities, including modification of habitats and introduction of animals. In the Humbolt Current upwelling ecosystem, starting in the mid 1970s, the Humboldt Penguin (Spheniscus humboldli) colony at Pájaro Nińo Island, central Chile, has undergone major modifications, including its joining to the mainland by a causeway and the removal of its pine forest. Although detrimental effects were expected, penguins continued breeding and the modifications provided new nesting habitats in which reproductive success has been similar to that observed in natural habitats. Additionally, the island holds today substantial numbers of breeding Chilean Pelicans (Pelacanus thagus) and Kelp Gulls (Larus dominicanus) which have also been able to use the modified habitats. Although local residents and tourists sporadically use the causeway to reach the island, human disturbance is kept to low levels. Some terrestrial mammals have been able to reach the island and are responsible for some degree of habitat degradation and predation. Despite these disturbances, Pájaro Niño Island is one of the most important breeding sites for Humboldt Penguins, Kelp Gulls and Chilean Pelicans in central Chile. Received 28 April 2000, accepted 8 May 2000.