The nighttime sky is increasingly illuminated by artificial light sources. Although this ecological light pollution is damaging ecosystems throughout the world, the topic has received relatively little attention. Many nocturnally migrating birds die or lose a large amount of their energy reserves during migration as a result of encountering artificial light sources. This happens, for instance, in the North Sea, where large numbers of nocturnally migrating birds are attracted to the many offshore platforms. Our aim is to develop bird-friendly artificial lighting that meets human demands for safety but does not attract and disorient birds. Our current working hypothesis is that artificial light interferes with the magnetic compass of the birds, one of several orientation mechanisms and especially important during overcast nights. Laboratory experiments have shown the magnetic compass to be wavelength dependent: migratory birds require light from the blue-green part of the spectrum for magnetic compass orientation, whereas red light (visible long-wavelength) disrupts magnetic orientation. We designed a field study to test if and how changing light color influenced migrating birds under field conditions. We found that nocturnally migrating birds were disoriented and attracted by red and white light (containing visible long-wavelength radiation), whereas they were clearly less disoriented by blue and green light (containing less or no visible longwavelength radiation). This was especially the case on overcast nights. Our results clearly open perspective for the development of bird-friendly artificial lighting by manipulating wavelength characteristics. Preliminary results with an experimentally developed bird-friendly light source on an offshore platform are promising. What needs to be investigated is the impact of bird-friendly light on other organisms than birds.

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VER 60 MILLION BIRDS, OF MANY species, cross the North Sea twice eachyear. Light has a significant impact on migratory birds at sea as it can attract and trap birds at large illuminated structures such as offshore platforms. In this article, we study the behavior of birds around offshore platforms and test the effect of the presence of lighting, the intensity and type of lights, and the light color on bird behavior. We developed a "bird-friendly" light spectrum that can be applied offshore to provide safe lighting for both humans and birds. We present the results of a field demonstration test involving the exchange of lights to the new color on a gas production platform. We also demonstrate our system's compliance with explosion safety requirements. It is expected that the bird-friendly lighting will become the new standard for any installation situated in areas with bird migration. 56

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