Issues

Cover: Chicken performing two-choice colour discrimination. Birds use colour in many behaviours, such as finding food and evaluating partners. They have impressive physiological adaptations for colour vision, such as tetrachromacy and coloured oil droplets. However, little is known about the limits of bird colour vision, such as the light intensities in which they can use colour and the smallest colour difference they can discriminate. Olsson et al. (pp. 184−193) tested these limits with behavioural experiments in chicken. The results indicate that high noise levels in visual processing limit bird colour vision and that chickens can still see colour in bright moonlight. Photo credit: Peter Olsson.