Birds in southern Öresund in relation to the wind farm at ... - Vattenfall

45
40
35
30
25
20
15
10
5
0
Birds/km 2
Mergus serrator
Winter
2006(3) 2008(1) 2009(4) 2010(1) 2011(3)
52
Outer
Buffer
Windfarm
Fig. 32. Densities (individuals / km 2 ) of Red-breasted Merganser Mergus serrator based on
aerial surveys during winter in different zones around the wind farm at Lillgrund in different
years. Number of surveys in brackets.
Täthet (individer/km 2 ) av småskrake Mergus serrator under vintern inom olika zoner runt
Lillgrunds vindkraftpark under olika år baserade på flyginventeringarna. Antalet
inventeringar inom parentes.
Overall Jacob’s indices showed qualitatively a general decrease in preference for both the
wind farm area and the buffer zone between pre- and post-construction periods (Table 4).
Data from the aerial surveys showed a weak avoidance already before the wind farm was
constructed (D = -0.26) and a somewhat stronger avoidance with the farm in operation (D =
-0.42). Boat survey data showed a change from preference (D = 0.41) to weak avoidance (D =
-0.27). For the buffer zone the changes were in the same direction, from preference (D = 0.22
and 0.47) to expected use (D = 0.07 and 0.03).
A separation of the indices for different years gives a less clear picture as the two survey
methods yield at least partly different results (Fig. 32). The boat survey data clearly indicates
change from preference for both the wind farm area and the buffer zone during the preconstruction
period to, mainly, avoidance for both parts with the wind farm in operation. The
aerial survey data show elements of the same story for the wind farm area in some postconstruction
years but not in all. According to this data set the buffer zone is used as expected
or weakly preferred in most years. No direct indications of habituation is given by the indices,
instead variation between years in the distribution of birds seem to be large.
We conclude that we can not see any major impact from the wind farm on the occurrence of
Red-breasted Mergansers in the area. Instead of just avoiding the wind farm, numbers have
been lower in the whole study area in the post- compared to the pre-construction years. Such