Sexual selection and the perception of colour

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Birds, like humans, respond to both colours and patterns displayed by other individuals when making decisions during social interactions about who to mate, cooperate, and fight with. Research over the past two decades has contributed immensely to our understanding of those colour and pattern signals, and we now have good evidence that variation in colour signals displayed by birds influences their lifetime reproductive success because those signals can reveal the health, condition, motivation, and experience of the signaller and that information is used by actual and potential mates when deciding on who to mate with and how much assistance to give that mate with parental care. Researchers have also developed sophisticated ways of measuring those signals, thanks in part to the development of relatively inexpensive reflectance spectrometry, image analysis, and computer programs for data management, colour modelling and statistical analysis. What is less well known are the limits of perceptual abilities that influence exactly what birds can perceive and respond to. We know, for example, that birds can see all the colours that we can see plus colure we cannot see in the ultraviolet part of the spectrum, but we know relatively little about their abilities to discriminate between colours, especially when those colours are only subtly different. Nor do we know how that ability to discriminate among different colours influences the evolution of colour patterns used in signalling. This research proposal addresses both of those problems with lab and field studies on a carefully selected group of species that display different colours, live in different environments, have a variety of mating systems, and are taxonomically diverse. We have chosen several of these species for study because their retinal physiology has been studied so we can predict with some accuracy what parts of the spectrum their eyes are most sensitive to, and as a result their visual processes can be modelled mathematically. Those visual models make predictions about colour discrimination that we will test with behavioural experiments. Using brain imaging technologies we will also map the intensity of responses to different colours as a measure of colour preferences. The results of this research will help define the mechanisms underlying the evolution of colours and colour preferences in birds. We know that some colours are displayed more often than others by birds, and our research will determine whether that range of colours is determined by the constraints on their visual system. Our findings will have broad ranging implications for the evolution of colour and pattern preferences in other animals, including humans.