A seabird and wetland reserve in the inner Oslofjord, protected in 1992 and extended with the neighbouring island of Heggholmen in 2008. Over 160 bird species have been recorded on the islands, and the bay between Gressholmen and Rambergøya is an important breeding and feeding area for seabirds; all boat traffic is prohibited during the breeding season from 1 April to 15 July.
See live sightings at Gressholmen-Rambergøya naturreservat →