Abstract:Populations of soaring birds are often impacted by wind-power generation. Sex and age bias in turbine collisions can exacerbate these impacts through demographic changes that can lead to population decline or collapse. While several studies have reported sex and age differences in the number of soaring birds killed by turbines, it remains unclear if they result from different abundances or group-specific turbine avoidance behaviours, the latter having severer consequences. We investigated sex and age effects o… Show more
“…S1 ), likely reflecting the most common turning angles of birds actively avoiding wind turbines when previously in a collision trajectory. Previous analyses with subsets of this data showed that birds exhibited inflated densities around 700–800 m from the wind turbines 10 , 13 , probably corresponding to trajectory changes with similar turning angles intended to avoid approaching wind turbines further. This pattern was also observed in other migrating raptors tracked by radar (see Fig.…”
Section: Methodsmentioning
confidence: 83%
“…1 ). Further details on field procedures and tracking equipment can be found in earlier publications with subsets of these data 10 , 13 , 19 . Figure 1 Left panel shows the spatial distribution of bird and turbine locations in the study area between Cadiz and Tarifa (southern Spain).…”
Section: Methodsmentioning
confidence: 99%
“…Birds generally avoid getting close to wind turbines, although the distance at which they tolerate the presence of turbines varies between species and spatiotemporal contexts 7 . Recent studies on soaring birds have established the presence of clearly defined thresholds to approaching wind turbines 8 – 13 . However, it remains unclear how these thresholds are established, and which variables trigger further approaches that may lead to collisions.…”
Section: Introductionmentioning
confidence: 99%
“…(2) Are flight directions near wind turbines influenced by wind direction and speed, uplift, turbine height and bird sex and age? We predict that: (1) birds will be less frequently oriented towards turbines as they fly closer and at low altitude (shown before for other raptor species 8 , 12 ); (2) bird directions will not be affected by turbine proximity when they fly higher than the rotor blades (shown before for other raptor species 12 , 15 ); (3) birds will be oriented more often towards turbines in areas rich in uplift, as they may compromise on avoidance to optimize the use of uplift 5 , 16 ; (4) birds will be less frequently oriented towards turbines when the wind is blowing in that direction in order to avoid being dragged into the rotor swept zone (this hypothesis has not yet been tested or suggested); (5) birds will be less frequently oriented towards larger than smaller turbines as the former have greater visual impact, although earlier studies were unable to prove this hypothesis 2 ; (6) sex and age will not influence flight directions, as similar turbine displacement patterns were found in different sexes and age classes of this species 13 .…”
Wind energy production has expanded as an alternative to carbon emitting fossil fuels, but is causing impacts on wildlife that need to be addressed. Soaring birds show concerning rates of collision with turbine rotor blades and losses of critical habitat. However, how these birds interact with wind turbines is poorly understood. We analyzed high-frequency GPS tracking data of 126 black kites (Milvus migrans) moving near wind turbines to identify behavioural mechanisms of turbine avoidance and their interaction with environmental variables. Birds flying within 1000 m from turbines and below the height of rotor blades were less likely to be oriented towards turbines than expected by chance, this pattern being more striking at distances less than 750 m. Within the range of 750 m, birds showed stronger avoidance when pushed by the wind in the direction of the turbines. Birds flying above the turbines did not change flight directions with turbine proximity. Sex and age of birds, uplift conditions and turbine height, showed no effect on flight directions although these factors have been pointed as important drivers of turbine collision by soaring birds. Our findings suggest that migrating black kites recognize the presence of wind turbines and behave in a way to avoid then. This may explain why this species presents lower collision rates with wind turbines than other soaring birds. Future studies should clarify if turbine avoidance behaviour is common to other soaring birds, particularly those that are facing high fatality rates due to collision.
“…S1 ), likely reflecting the most common turning angles of birds actively avoiding wind turbines when previously in a collision trajectory. Previous analyses with subsets of this data showed that birds exhibited inflated densities around 700–800 m from the wind turbines 10 , 13 , probably corresponding to trajectory changes with similar turning angles intended to avoid approaching wind turbines further. This pattern was also observed in other migrating raptors tracked by radar (see Fig.…”
Section: Methodsmentioning
confidence: 83%
“…1 ). Further details on field procedures and tracking equipment can be found in earlier publications with subsets of these data 10 , 13 , 19 . Figure 1 Left panel shows the spatial distribution of bird and turbine locations in the study area between Cadiz and Tarifa (southern Spain).…”
Section: Methodsmentioning
confidence: 99%
“…Birds generally avoid getting close to wind turbines, although the distance at which they tolerate the presence of turbines varies between species and spatiotemporal contexts 7 . Recent studies on soaring birds have established the presence of clearly defined thresholds to approaching wind turbines 8 – 13 . However, it remains unclear how these thresholds are established, and which variables trigger further approaches that may lead to collisions.…”
Section: Introductionmentioning
confidence: 99%
“…(2) Are flight directions near wind turbines influenced by wind direction and speed, uplift, turbine height and bird sex and age? We predict that: (1) birds will be less frequently oriented towards turbines as they fly closer and at low altitude (shown before for other raptor species 8 , 12 ); (2) bird directions will not be affected by turbine proximity when they fly higher than the rotor blades (shown before for other raptor species 12 , 15 ); (3) birds will be oriented more often towards turbines in areas rich in uplift, as they may compromise on avoidance to optimize the use of uplift 5 , 16 ; (4) birds will be less frequently oriented towards turbines when the wind is blowing in that direction in order to avoid being dragged into the rotor swept zone (this hypothesis has not yet been tested or suggested); (5) birds will be less frequently oriented towards larger than smaller turbines as the former have greater visual impact, although earlier studies were unable to prove this hypothesis 2 ; (6) sex and age will not influence flight directions, as similar turbine displacement patterns were found in different sexes and age classes of this species 13 .…”
Wind energy production has expanded as an alternative to carbon emitting fossil fuels, but is causing impacts on wildlife that need to be addressed. Soaring birds show concerning rates of collision with turbine rotor blades and losses of critical habitat. However, how these birds interact with wind turbines is poorly understood. We analyzed high-frequency GPS tracking data of 126 black kites (Milvus migrans) moving near wind turbines to identify behavioural mechanisms of turbine avoidance and their interaction with environmental variables. Birds flying within 1000 m from turbines and below the height of rotor blades were less likely to be oriented towards turbines than expected by chance, this pattern being more striking at distances less than 750 m. Within the range of 750 m, birds showed stronger avoidance when pushed by the wind in the direction of the turbines. Birds flying above the turbines did not change flight directions with turbine proximity. Sex and age of birds, uplift conditions and turbine height, showed no effect on flight directions although these factors have been pointed as important drivers of turbine collision by soaring birds. Our findings suggest that migrating black kites recognize the presence of wind turbines and behave in a way to avoid then. This may explain why this species presents lower collision rates with wind turbines than other soaring birds. Future studies should clarify if turbine avoidance behaviour is common to other soaring birds, particularly those that are facing high fatality rates due to collision.
“…We used the data from 68 of the 71 studies to assess the current knowledge on bird displacement, with a total of 286 trials. We excluded three studies from this analysis [24][25][26], whose information was duplicated, at least partially, in other works. We stress that, as the considered studies implemented quite variable methodological approaches (see previous section), comparisons across studies and taxa should be conducted with caution.…”
Section: Current Knowledge On Bird Displacement By Wind Turbinesmentioning
Wind energy developments can be responsible for negative impacts on birds, including displacement. In this study we performed a systematic review of the literature available on bird displacement due to wind turbines, both onshore and offshore, to: (i) assess overall trends in scientific research; (ii) review the existing knowledge; and (iii) outline recommendations for future studies on this topic in order to overcome the major gaps and limitations found. Our results are based on 286 trials extracted from 71 peer-reviewed studies. The literature on this topic has increased in the past decade but is concentrated in Europe and United States, despite the fact that the wind industry has worldwide coverage. Open habitats—as agricultural fields and grasslands—were the most represented and Accipitriformes, Galliformes, Charadriiformes, Anseriformes and Passeriformes were the most frequently studied taxa. Displacement was recorded in 40.6% of the trials, and Gaviiformes, Anseriformes, Suliformes, Accipitriformes and Falconiformes were the most affected groups. Pelecaniformes, Passeriformes and Charadriiformes were the groups for which no significant effects were more often observed. We provide a list of recommendations, focused on study design, reporting and result dissemination, that should contribute to more robust conclusions of future studies on this topic.
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