|Taste the rainbow: plasma carotenoids and rictal flange color in urban, rural, and captive nestlings|
|Rebecca Fox, Christine Lee. Transylvania University, Lexington, KY, United States
The rapid spread of urbanization has created habitats that pose novel challenges for organisms including variation in the availability of dietary nutrients. When organisms use dietary pigments like carotenoids in signaling, differences in diet quality across urban and rural environments may influence behavior and life-history independently of effects on somatic growth and health. This may be particularly true for signals expressed early in development that influence parental provisioning, as in the case of carotenoid-based rictal flange color in house sparrow nestlings. We used blood sampling and the analysis of digital photographs to compare plasma carotenoid levels and rictal flange color in free-living house sparrow nestlings on a farm (rural) and at a site near downtown Lexington, KY (urban), and compared them to captive nestlings reared on a relatively carotenoid-deficient diet. As predicted, captive nestlings had the palest flanges and lowest levels of circulating carotenoids, and rural nestlings had yellowest flanges and the highest levels of circulating carotenoids. We also tested for an association between body condition and circulating carotenoids or flange color.