Exploratory and descriptive study on nutritional characteristics and quality of eggs from Chilean partridge (Nothoprocta perdicaria).

This work aims to contribute more information on tinamou eggs by performing an exploratory and descriptive study of some of their nutritional and quality characteristics. The chemical composition of tinamou egg showed a high protein content in white (85% dry basis) and high lipid concentration in yolk (52% db). The iron (Fe) content in white was higher than hen egg (0.47 mg/100 g) and this could be associated with the observed pinkish color of the white. As in the hen egg, the major fatty acids in tinamou yolk were: oleic (39%), linoleic (23%) and palmitic (20%). The cholesterol content of tinamou was 21.2 mg/g of yolk, and 100 g of whole egg provides 589 mg of cholesterol. As in the hen egg, tinamou egg white showed high levels of lysine, sulfur-containing amino acids, threonine and valine with respect to the recommended allowance for an adult man. All essential amino acids with the exception of histidine cover the adult requirements. The shell inorganic composition of these eggs is calcium carbonate and the morphology was similar to other avian eggs. Tinamou egg is small and elongated, with a dark brown color. The eggshell is thinner and experiences more deformation but less breaking strength than hen eggshell.

Aerobic performance in tinamous is limited by their small heart. A novel hypothesis in the evolution of avian flight.

Some biomechanical studies from fossil specimens suggest that sustained flapping flight of birds could have appeared in their Mesozoic ancestors. We challenge this idea because a suitable musculoskeletal anatomy is not the only requirement for sustained flapping flight. We propose the "heart to fly" hypothesis that states that sustained flapping flight in modern birds required an enlargement of the heart for the aerobic performance of the flight muscles and test it experimentally by studying tinamous, the living birds with the smallest hearts. The small ventricular size of tinamous reduces cardiac output without limiting perfusion pressures, but when challenged to fly, the heart is unable to support aerobic metabolism (quick exhaustion, larger lactates and post-exercise oxygen consumption and compromised thermoregulation). At the same time, cardiac growth shows a crocodilian-like pattern and is correlated with differential gene expression in MAPK kinases. We integrate this physiological evidence in a new evolutionary scenario in which the ground-up, short and not sustained flapping flight displayed by tinamous represents an intermediate step in the evolution of the aerobic sustained flapping flight of modern birds.