Condition-dependent signal reception: limitations and functions of carotenoids in avian color vision

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Animals use a diversity of signals for communication (e.g. songs, colors), many of which are honest indicators of their worth as a mate or rival. However, the ways that animals perceive the world and receive transmitted signals may also be linked to their quality (e.g. health, condition), and such control of signal reception could impact the evolutionary pace and directions of animal communication systems. This research will involve investigations of the degree to which the color-visual sensory system of a songbird species (the house finch, Carpodacus mexicanus) is impacted by environmental factors, including diet, disease, and light exposure, and affects critical behavioral tasks like food selection and mate selection, both of which involves color preferences. Condition-dependence of color vision will be explored by tracking accumulation of the types and amounts of carotenoid pigments (e.g. the orange colorants of carrots) dedicated to the retina, where they are thought to filter light, protect the eye from photodamage, and tune color visual sensitivity. This approach provides a key molecular link between color vision and color production, which in house finches and many other animals occurs in the form of red, orange, and yellow carotenoid pigments whose supplies in feathers are also limited and condition-dependent. The biochemical, nutritional, and behavioral approaches taken in this research will enrich understandings of (a) the suite of benefits conferred by antioxidant nutrients in animals, (b) resource allocations and trade-offs in the context of animal communication, and (c) the coevolutionary mechanisms governing sexual traits and preferences in animals, tracked in a common chemical currency. The urban nature of the field research also affords the opportunity to involve local schoolteachers and children in data collection and science training, so that they may test first-hand the impacts of human encroachment on the communication system and viability of a desert-adapted organism.