Predicting the Weather-Dependent Collision Risk for Birds at Wind Farms - Wind and Wildlife - page 14

Fig. 5 Observed altitude plotted against distance to closest wind turbine for common scoters at
Horns Rev. The different colors indicate head winds ( red ), tail winds ( blue ) and side winds ( green ).
The rotor height ( lowest tip ) of the turbines at Horns Rev 2 is indicated with a dashed black line
Rødsand II wind farm area above rotor height in tail winds and at rotor height in
head winds (Fig. 9 ).
The collision model indicated that 42 % of the red kites entered the wind farm
area during a season causing an estimated collision rate of 9 birds. Thus, the impact
of collisions of red kites at this wind farm would constitute a level approximately
1/16 of the regional threshold for sustainable collision-induced mortality (79 birds).
Discussion
The two studies on weather dependent collision risks for birds at coastal wind farms
in Denmark provided substantial new information. First, the application of gener-
alised additive mixed models on the rangefinder track data clearly showed that wind
direction and speed, humidity and air temperature are correlated with the flight
altitude and thus affected potential collision risk of several species of landbirds and
seabirds. The flight models constitute a novel method for risk assessment in relation