Distribution and numbers of wintering sea ducks ... - Lunds universitet

ters, restricted to the innermost bays of the archipelagos.
The 2010 winter was a contrast to 2009, being
the coldest winter since 1987. The archipelagos got
covered by ice early and at the time of the survey
there was compact ice from the Stockholm archipelago
to finland. The major offshore banks were
surveyed during the winter but parts of the archipelagos
could not be covered until the first days of
April. Coverage of the counts in 2010 is seen from
figure 2.
2011 was another cold winter with very cold
weather already in December 2010. There was
open water along the south coast in Scania, but the
archipelagos from Kalmarsund in the south were
totally frozen and there was only small areas of
open water in the outermost parts of the archipela-
figure 2. Coverage of the aerial surveys in offshore Swedish
waters in the winters 2009, 2010 and 2011. Black lines =
line transects, red dots = area-based counts. for ice cover in
2011, see figur 3.
Täckningen med flyginventeringar i svenska utsjöområden
vintern 2009. Svarta linjer = linjetaxeringar, röda punkter =
områdesbaserade inventeringar. För istäcke 2011, se Figur 3.
gos north of Kalmarsund (figure 2). The ice extended
east over the Baltic Sea and the important
offshore areas in the Baltic republics were all icecovered
(figure 3).
The southern parts of the Baltic could be covered
during the winter proper, whereas the archipelagos
further north could not be covered until
the first days of April in some cases. This is of no
problem for the long-tailed Ducks that leave the
Baltic in May but the late surveys could not be
used for the Eider and the Scoters. These species
are however present in small numbers in these
areas during the winter as shown by the countrywide
surveys of the archipelagos. The offshore
surveys in 2009 were for some species supplemented
by observations from the annual midwinter
counts for some inshore areas (mainly on west
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