The tinamous is a ancient family of flying birds known to have the smallest heart to body ratio compared to birds and mammals and is more similar to that of reptiles.

The heart is the main regulator of cardiorespiratory function which in turn is the major determinant of the metabolic rate and thus thermoregulation in endotherms. A small heart to body ratio provide a limitation of cardiorespiratory capacity and thus impose challenges to maintain an elevated metabolic rate, especially in a high altitude hypoxic environment.

The focus of this study was to determine how the Ornate tinamous, Nothoprocta ornata, copes with living in and high altitude environment while having a small heart to body ratio.