Spring staging of Eiders Somateria mollissima in some Swedish east coast archipelagos and at Gotland 2009 and 2010.

The Eider Somateria mollissima is a common
breeding species in the Baltic. In 2008, Ottosson
et al. (2012) estimated that the breeding population
of Eiders in the archipelagoes of the four Swedish
counties of Kalmar, Östergötland, Södermanland
and Stockholm was in the order of 103 000 pairs,
whereas the breeding population around Gotland
was about 6000 pairs. The distribution of breeding
Eiders in several regions is well known from
extensive surveys (cf. Gezelius 2012, Sveriges Ornitologiska
Förening 2009). On the other hand, the
distribution of staging Eiders in early spring has
not been studied on a regional level before.
During 2009‒2011, extensive offshore surveys
were undertaken in the Baltic (Nilsson 2012, Skov
et al. 2011). The main target species was the Longtailed
Duck Clangula hyemalis. For various reasons
some areas (the east coast archipelagos from
Gävle–Kråkelund in 2009 and eastern Gotland in
2010) were surveyed during the time for the spring
migration of the Eider (which is still winter for the
Long-tailed Ducks, leaving the Baltic in May). In
this short contribution I present the results from
these surveys for the Eider to give first snapshots
of the distribution of the species along the Baltic
coast of Sweden during the migration period.