Effects of carotenoid supply on escape flight responses in zebra finches, Taeniopygia guttata

Dietary carotenoids perform several important roles in animals including as antioxidants, immunostimulants and pigments responsible for sexual signals. However, carotenoids may be in limited supply because of foraging constraints and/or physiological trade-offs in their utilization. Studies of birds and fish have shown that females frequently prefer to mate with carotenoid-rich males, which may serve to ensure the acquisition of a healthier mate. Evidence suggests that antioxidant and immune defences can be constrained by carotenoid availability, but we still lack information about the functional consequences of such carotenoid limitation for health, or any measure of physiological performance at the behavioural level. We tested whether carotenoid availability influenced escape flight responses in captive male zebra finches. Birds were fed a control or carotenoid-supplemented diet for 8 weeks, before measurements of escape flight responses from a release chamber after a startle stimulus. Carotenoid supplementation enhanced flight performance: carotenoid-supplemented birds had shorter flight times than controls. In addition, compared to controls, carotenoid-supplemented birds less often required a repeat startle stimulus to elicit escape flight, and emerged sooner from the release chamber after a startle stimulus. Such effects of carotenoids could be ecologically important, since flight take-off performance is thought to be an important determinant of predator evasion and foraging, and thus of survival probability and the capacity to provide parental care. We discuss various putative physiological mechanisms to explain how carotenoids may influence flight behaviour and performance.