Action: Paint wind turbines to increase their visibility
A single ex situ experiment found that thick black stripes running across a wind turbine’s blades made them more conspicuous to an American kestrel than control (unpatterned) blades, but that other designs were less visible, or indistinguishable from controls.
Wind turbines can have a detrimental impact on birds both through direct collisions with the blades or because the vortices created force birds to the ground. Direct collisions may be reduced if birds can clearly see and avoid blades.
Supporting evidence from individual studies
A randomised, controlled ex situ experiment on an American kestrel Falco sparverius (McIsaac 2001) found that it could discriminate between a control stimulus and an image of rotating wind turbine blades better if the blades were painted with two thick black bands running across the width of the blade (a visibility ratio of 2.4 in bright light, decreasing to 1.5 in low light, no difference in very low light). Blades with narrow black bands running across the width of the blade were less conspicuous in bright light (ratio of 0.1) and were indistinguishable in low light. A pattern of three stripes running the length of the blade were not significantly more or less conspicuous than plain white blades. Both the control (grey blade rotating in front of a grey background) and experimental stimuli rotated at 30 rpm.