Tvarminne

Tvärminne (65.081°N x 22.748°W) in the southwestern archipelago of Finland, Baltic Sea, consists of a mosaic of islands of variable size. There are small open granite islets characterized by bare rocks and sparse grass or juniper, as well as larger islands dominated by pine forest and juniper shrubs. The nearby Tvärminne Zoological Station facilitates fieldwork here, and most islands are protected by a prohibition on landing, allowing visits only for researchers.

The most common breeding bird is the common eider: nearly a thousand eiders were breeding in the core study area of ca 40 islands in the 1990s, but their numbers have quickly dwindled due to intense predation particularly by the rapidly increasing white-tailed eagle. This provides a unique opportunity to study predator-prey interactions at this site. Other common seabirds are mute swans, greylag and barnacle geese, several species of gulls and terns, as well as smaller numbers of oystercatchers, goosanders, mallards and tufted ducks.