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

Herring Gull Larus argentatus
The Herring Gull was the most numerous gull species in the southern part of Öresund during
the winter season, other species were only found in smaller numbers. Normally, the Herring
gulls appear in small groups and singly well spread over the entire study area. Sometimes
larger concentrations occur, mostly in connection with fishing boats. Larger flocks of Herring
Gulls was also found at the roosting site on Måkläppen south of Falsterbo at several aerial
surveys. Maximum counts from the aerial surveys was about 500 in the northern area, but
close to 1300 were counted here during one early boat survey Fig. 34, 35).
No clear pattern in the distribution of the Herring Gulls related to the construction of the wind
farm was found in the aerial survey data (Fig. 36). The boat survey data on the other hand
clearly show a decreased use of the wind farm area during the operational phase (Fig. 37).
The densities of Herring Gulls in the three different zones at the Lillgrund windfarm showed
much variation between years without any clear pattern (Fig. 38). Some high densities found
were related to fishing activities in the area leading to a concentration of gulls. Number of
Herring Gulls actually counted at the aerial surveys varied between 0 and 3 for the windfarm
area, 2 and 35 for the buffer zone and 1 to 430 for the outer reference area.
The overall Jacob’s indices did not show any clear results connected to the wind farm for the
Herring Gull (Table 4). The aerial survey data showed a change from avoidance (D = -0.36)
pre-construction to expected use (D = 0.03) for the operational phase for the wind farm area.
The boat survey data showed a weak avoidance for the pre-construction period (D = -0.11)
and a stronger avoidance with the farm in operation (D = -0.71) for the wind farm area. The
buffer zone was used according to expectation or avoided during pre-construction (D = 0.06
and -0.20 based on aerial and boat survey data respectively). With the farm in operation this
area was avoided (D = -0.27) according to the aerial survey data, but preferred (D = 0.46)
based on boat survey data.
A closer look at the Jacob’s indices from separate year do not add much more to the story,
although the boat survey data clearly indicate that the wind farm area has been avoided after
the farm came into operation (Fig. 39). The main explanation for this is probably that fishing
vessels no longer can use the area where the wind farm is today.
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