An animal deterrence system projects polarized light in order to deter animals. The light may be plane polarized light and the polarization may be varied over time. The system is particularly suited to deterrence of birds, but may also find application in deterrence of other animals sensitive to polarization of light, such as bees and wasps. The system may be used on vineyards or orchards, or around airports, or in any other place where birds are problematic.