Status of Breeding Birds at Observatorio and Goffré Islands, Argentina

Continental islands are often sites of low diversity and endemism, as well as important areas for the protection of bird populations, especially seabirds. On Isla Observatorio and the Ano Nuevo Islands, in the Southwestern Atlantic, the latest assessment of avifauna dates from more than 20 years ago. In this study, we use a combination of methods to update the status of the main seabird colonies and the most abundant avian terrestrial predator at Observatorio and Goffre Islands during the breeding season. In only 4.5 km(2), the islands would harbour similar to 90,000 breeding seabirds. Seabird colonies occupied different areas of the islands and varied in their population status, with Imperial Shags (Leucocarbo atriceps) showing an increase and Southern Giant Petrels (Macronectes giganteus) a decrease according to the last surveys. Magellanic Penguin (Spheniscus magellanicus) population estimations also suggest a decrease but the last survey was based on total, and not on occupied nest sites. We recorded and assessed one new breeding species: The globally near-threatened Striated Caracara (Phalcoboenus australis), which has an important breeding population of around 15 territorial pairs at Observatorio Island. These islands appear to be an important regional bird site and future studies would determine their trends and threats, especially those related with invasive species.