Tropical birds have a “slower pace of life,” with lower rates of whole-animal metabolism, smaller metabolically active organs, and lower cellular metabolic rates than their temperate counterparts. Oxidative stress is a physiological mechanism that may dictate differing life-histories such as those found between tropical and temperate birds. Oxygen is required to make ATP, resulting in the production of reactive oxygen species (ROS). If left unchecked, ROS can structurally alter proteins, induce mutations in DNA, and damage structural lipids. To combat accumulating oxidative damage, organisms have evolved an elaborate and costly antioxidant system that serves to sequester ROS before they wreak cellular havoc. We examined whether oxidative stress would differ between tropical and temperate birds. We used isolated primary dermal fibroblasts and pectoralis muscle tissue for measurements. We measured four aspects of oxidative stress in primary fibroblasts – reduced glutathione (GSH) concentration, ROS production, mitochondrial content, and lipid peroxidation (LPO) damage. We found no significant differences in the four variables between temperate and tropical birds.. In muscle tissue, we measured catalase (CAT), superoxide dismutase (SOD) glutathione peroxidase (GPx) activity, peroxyl and hydroxyl scavenging capacity, and LPO damage. We found that peroxyl scavenging capacity was significantly higher in tropical birds compared with temperate birds.