Why the superb physiological capacity of birds matters.

Among vertebrates, birds undertake the longest, fastest and highest migrations of any taxonomic group, largely due to their unique cardiorespiratory system, which permits for very large rates of gas exchange. Managing resultant elevated production of reactive oxygen species, and thus oxidative stress, has meant that birds can largely avoid pathologies relating to major medical challenges that now probably account for the majority of global healthcare spending. Hypoxia underlies most critical illnesses faced by humans, but the avian cardiorespiratory system can supply far more oxygen per unit of time than any mammal. Birds have high circulating glucose levels, but have adaptations to cope with the elevated production of oxidative stress brought about by hyperglycaemia. Birds also avoid the inflammatory responses brought about by obesity in humans when they seasonally gain huge fat stores. Lastly, birds live four times longer than similarly sized mammals, with seasonal endogenous muscle hypertrophy, and some birds even increase telomere length with age. A new frontier of 'physiologging' is emerging, making use of technologies for medical use, but that provide novel parameters for better understanding the biomechanics, energetics and ecology of a range of species. These physiologging tools are likely to provide insight into avian physiology, biomechanics and ecology including their ability to spread disease, as well as each of the medical challenges detailed in this Commentary. By virtue of their physiological capacity, the study of avian physiology is a critical area for future discovery and research using applied and interdisciplinary areas of biomechanics, ecology and physiology.