Bird Vision: Spatial acuity and colour discrimination in bright and dim light

TL;DRAbstract

Birds use vision to guide navigation, foraging and mate choice, and studies of the limitations in bird visual perception are most helpful for the understanding of bird ecology. Here, I present four studies of bird vision in bright and dim light. Paper I is a quantification of how sensitive colour vision modelling is to variation in data, such as the spectral sensitivity of photoreceptors and receptor noise, which are used as model parameters. In Papers II and III, I have studied budgerigars (Melopsittacu undulatus), which are strictly diurnal, and Bourke’s parrots (Neopsephotus bourkii) that are diurnal but also active during twilight. Paper II shows that the intensity limit of colour vision and the optical sensitivity of single photoreceptors are similar in both species. Both parrots need more light to see colours (between 0.1-0.4 cd/m2) than other vertebrates (e.g. 0.01 cd/m2 for humans). In Paper II, it was also found that Bourke’s parrots have larger eyes and retinas with a higher

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