This environmental impact assessment for Kriegers flak ... - Vattenfall

130 CONSEQUENSES OF THE WIND FARM
12.4.3 Birds
The occurrence of birds is described in Chapter 11.6.3.
12.4.3.1 Impact
The wind farm may give cause to the following impact
on birds:
a) Risk of collisions
b) Disturbance of staging and foraging water fowl
c) Barrier for migrating birds
d) Loss of habitat
a) Risk of collisions
In theory, all birds ß ying below 200 metres are subject
to the risk of collision. Looking at the radar measurements
carried out by the company, between 60 and 64
% of birds registered during day time, belong to this
category. For birds registered during night time, the
number was 30 to 39 %.
Birds migrating during day time will be less affected
as they can see the hazards earlier and ß y
around them.
As the wind turbines will be ß oodlit, it will in
general also be possible to see them during night time.
Critical situations with added collision risk will primarily
occur during the night with sudden fog/rain or
strong winds occurring.
Studies of collisions between birds and wind turbines
constitutes a lot of the material that deals with
the impact of wind turbines. European studies show
that the impact of wind turbines on birds through collisions
are minimal in the areas that have been studied
and in the habitats that are of interest for establishing
wind farms. These studies have been criticised for having
been made in areas with single turbines and often
burdened by some sort of methodical problem, making
the results difÞ cult to interpret.
A recent study of the risk of collision at Utgrunden
and Yttre Stengrund (Jan Pettersson and Thomas Stalin)
however shows that even in the case with a greater
number of turbines (seven and Þ ve respectively), the
collision risk is minimal.
Before the seven wind turbines at Utgrunden were
installed, about 40 % of ß ights of a total of 125 058
eider ducks, ß ew in the area where the turbines later
were installed. When the wind farm had been installed
only 6 % of 192 751 (spring of 2001) and 7 % of 211
239 eider ducks (spring of 2000) ß ew through the area.
Observations at Utgrunden wind farm
Investigations at Yttre Stengrund showed the same
pattern. During the autumn of 2000, before the installation
of the wind turbines, 32 % of eider ducks under
ß ight ß ew through the area where the turbines later
were erected. During the autumn 2001, when the turbines
had been erected, only 2 % ß ew through the area.
Radar investigations were carried out during night
time and showed that the birds identify the turbines in
the dark and that they avoid them in the same way as
during day time.
Investigations at Utgrunden and Yttre Stengrund
showed that the birds, both during day and night time,
seemed to detect the turbines at a distance of 2 km.
The birds chose to pass at a relatively big distance of
500 to 1 000 metres from the turbines. Which side
of the wind farm that the birds chose depends on the
wind direction. It is very rare that the birds chose to
ß y above the wind turbines. During the whole time of
investigation, not a single collision was observed (see
picture on next page).
No collisions were observed during visual observations
during day time at the Danish wind farms Horns
Rev and Nysted.
The radar investigations carried out at Horns Rev
showed that only between 14 and 22 % of the birds
chose to ß y through the wind farm. At Nysted, the corresponding
Þ gure was 9 %.