Mink

The mink is not native to Sweden. It escaped from mink ranches during the 1900s and has since spread out over the entire country.
Threat to seabirds
At the same time that the mink was spreading along the coasts and archipelagos, the populations of many seabirds declined. Hunting by the mink is one possible explanation, since Swedish birds are not adapted to avoiding the danger from the new predator.