Zebra Finches use bright orange-red pigments called carotenoids, derived from their diet and made usable in mitochondria, in the colors of their beaks and legs. These displays are used by males to attract mates. Our aim is to lower the function of mitochondria in Zebra Finch males, and to observe the effect this has on carotenoid production. If there is a decrease in production, this will be evidence that carotenoid-based displays could be honest signals to females of mitochondrial fitness.