Tropical birds are usually placed in the “slow” end of the life-history continuum, and much of their physiology matches the trade-off between lifespan and reproduction. For example, they demonstrate lower whole-animal basal metabolic rates (BMR) and peak metabolic rates (PMR) compared with temperate birds, and at the cell level, tropical birds also have lower rates of oxygen consumption. Oxidative stress, a by-product of aerobic respiration, has yet to be fully elucidated to be linked to life-history theory. However, previous work suggests that tropical birds may have superior antioxidant capacity to birds that live in temperate areas. In the current study, we used muscle tissue from 35 species of tropical birds to measure total antioxidant capacity (hydroxyl scavenging capacity and peroxyl scavenging capacity), the activity of antioxidant enzyme catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx), and lipid damage (LPO). We correlated these measurements to body mass and found a significantly negative correlation between body mass and LPO and a marginally significant negative correlation with hydroxyl scavenging capacity. Interestingly, we also correlated our measurements to literature reported BMR measurements from 22 species included in our study and found no correlations. A negative correlation between body mass and LPO damage may be due to cellular muscle structure and mitochondrial content and structure within the muscle.

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