Disclosed is an animal or bird deterrence or repelling apparatus using light with varying polarisation effect over time. The apparatus includes a light source providing light in a wavelength range detectable by a target animal and a polariser, the apparatus configured to project polarised light over an area in which animals are to be deterred. The plane polariser filter varies the degree of polarisation by randomly varying the rate of rotation of the filter over time between 1-500 cycles per minute.
