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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 wholeanimal 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 dismulase (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. Received 6 October 2021. Accepted 24 May 2022. Key words: basal metabolism, life-history, muscle, oxidative stress, tropical birds. Las aves tropicales generatmente se ubican en el extreme- 'lento' del eontinuo dc la historia de vida. y gran parte dc su fisiologia coincide con el equilibrio cntrc la vida util y la rcproduccion. Por ejemplo, las avcs dcmucstran tasas metabolicas basalcs (BMR) y tasas metabolicas maximas (PMR) de animal complcto mas bajas en comparacion con las avcs dc clima templado y. a nivel cclular. las aves tropicalcs tambicn tienen tasas mas bajas dc consume- dc oxtgeno. El estres oxidativo, tin subproducto dc la respiration aerobica. atin no sc ba dilucidado por complcto para vincularlo a la tcoria dc la historia dc vida. Sin embargo, trabajos previos stigicrcn que las aves tropicalcs ptieden tcner una capacidad antioxidamc superior a las aves que viven en areas templadas. En cste estudio. utilizamos tcjido muscular dc 35 especies dc avcs tropicalcs para medir su capacidad antioxidamc total (capacidad de captacion dc hidroxilo y capacidad dc captacion dc peroxilo), la actividad de la enzima anlioxidante catalasa (CAT), la superoxido dismutasa (SOD), la glutation peroxidasa (GPx) y el dano de It'pidos (LPO). Correlaeionamos cstas medicioncs con la masa corporal y encontramos una correlation signiticativamente negativa entre la masa corporal y la LPO, y una corrclacion ncgativa marginalmente significativa con la capacidad de captacion de hidroxilo. C'uriosamente. tambien correlaeionamos nuestras mediciones con mediciones de BMR encontradas en la litcrattira para 22 especies incluidas en nucstro estudio y no encontramos correlacioncs. Una corrclacion ncgativa cntre la masa corporal y el dano por LPO pucde debcrsc a la cstructura muscular cclular. y al contcnido y cstructura mitocondrial dentro del musculo. Palabras clave: avcs tropicalcs. estres oxidativo. historia dc vida, metabolismo basal, musculo,, Variation in life-history events, such as growth rate, maintenance, body size, reproductive output, and timing reflect the crux of life-history theory, which states that a differential allocation of resources may [...]