BSEP116B Biodiversity in the Baltic Sea - Helcom

80
1,20
% successful breeding pairs
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10
1,00
0,80
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0,20
Reproduction success
0
1973
1975
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0,00
% successful breeding pairs Reproduction success
Figure 4.3.7. The development of reproductive parameters of the white-tailed eagle in Mecklenburg-
Western Pomerania, 1973–2008.
that a large proportion, about 12% of the birds,
had oil in the plumage (Larsson & Tydén 2005).
Although any kind of oil discharge from ships is
strictly prohibited in the Baltic Sea, chronic oiling
is most likely an important reason for the decline
of the European wintering population of the
long-tailed duck.
White-tailed eagle (Haliaeetus albicilla)
The white-tailed eagle breeds in coastal and
inland lake areas of all Baltic countries. These
countries, together with Norway, host the major
part of the European population, which currently
probably accounts for more than 50% of the
global population.
Although the white-tailed eagle is not a ‘true’
coastal species, it reaches remarkably high concentrations
in some coastal areas. The Odra
lagoon area, for example, has been known as
one of the last density centres during the first
half of the 20th century (Mizera 2002), and currently
still shows the highest density of breeding
pairs in Central Europe (Hauff et al. 2007). In
Lithuania, a concentration of breeding sites in the
Nemunas delta and around the Curonian Lagoon
is obvious (Dementavičius 2007). In Sweden also,
the major part of the population is found along
the coast (Tjernberg & Svensson 2007). In Finland,
the species is concentrated in the southwestern
coastal areas, but also occurs along the whole
coastline and around large inland lakes in Lapland
(SYKE 2008b).
At the beginning of the 20th century, as a consequence
of severe persecution, the white-tailed
eagle was close to extinction all around the Baltic
Sea. In Denmark, the species disappeared after
1911, in 1913 in Mecklenburg-Western Pomerania,
only 23 bp were known, and the Polish population
of that time was estimated at about 20 bp (Hauff
& Wölfel 2002, Mizera 1999). In Lithuania and the
Kaliningrad region of Russia, the white-tailed eagle
also disappeared for a long time.
Owing to protection measures against persecution,
the population started to recover during the 1920s,
but the positive trend was reversed from the mid-
1950s to the early 1980s by the harmful effects of
chemical pollutants (DDT and PCBs) on fertility and
reproductive success. The proportion of successful
breeding pairs dropped down to only 20–30%, and
the reproductive success to 0.2–0.4 fledglings per
breeding pair. As a consequence, the population
remained stagnant or even decreased. Owing to the
ban on DDT and other pesticides in the early 1970s,
the reproduction parameters started to improve at
the beginning of the 1980s, and returned to normal
levels in the mid-1990s (Figure 4.3.7).
Currently, the white-tailed eagle population is
increasing in all Baltic countries (Table 4.3.1, Figure
4.3.8). The species has also returned to territories
abandoned in the past (e.g., Lithuania in 1987,
Denmark in 1995). In recent years, a range expansion
to the west (western and southwestern parts of
Germany) has been observed, and in 2006 the first
breeding pair was recorded in the Netherlands.
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