Introduction
Argentavis was a large predatory bird that inhabited Argentina in the Miocene era about 6 million years ago, it had the wingspan of 7 meters and weighed as much as 70 to 72kg becoming the largest known flying bird on Earths natural history, this species belonged to a family knows as Teratornithidae, teratons fossil deposits date from the Miocene to Pleistocene, they were closely related to New World vultures (Vulturidae) and storks (Ciconiidae) (Chatterjee, Templin and Junior, 2007).
Anatomy and flight mechanisms
Various studies have been performed in computer software's to determine the lifestyle of this species in their natural environment, the computer program created a simulation where a specimen of this species would be subjected to different scenarios such as take-off, flight method and landing technique, in this simulations is taken to count the velocity of the wind current in the ecosystem and other climacteric variations such as seasons (Chatterjee, Templin and Junior, 2007)(Alexander,2007). Argentavis was near the theoretical limit size for safe gliding, flapping wings compared to gliding require a substantial amount of energy derived from the muscles, therefore the larger the bird is a greater amount of energy is needed to maintain the flapping motion (Chatterjee, Templin and Junior, 2007). Flight muscles in bird represent 17% of their total body weight, in case of the Argentavis it presented small pectoralis muscles since they are responsible for the downstroke of the wings, therefore it is unlikely it could flight by flapping, according to some studies these organisms were high-performance gliders, and it could achieve up to 84.6N/m2, 14N/m2 more than the California condor due to the larger body size of Argentavis (Chatterjee, Templin and Junior, 2007).
Hunting and flight
For these organisms to take off it needed to use a wind current in cliffs to glide, these winds needed to be in estimate greater than 1 m/s which would be common to find in the environment, when hunting it would most likely use thermal soaring, this flying mechanism is used by other modern birds of prey such as eagles, vultures among other species, it allows the bird to conserve energy by gliding in a circular motion gaining altitude or maintaining it due to the rising air heated by the ground, once achieved the maximum hight of the heat column Argentavis could glide to another air column nearby and repeat the same process increasing the possibilities of finding prey (Chatterjee, Templin and Junior, 2007).
Some fossil records were found in Argentine pampas and the Andean foothills, the pampas in the modern days present windy climate, and it is hypothesized that the wind condition was the same in the Miocene but the environment was significantly drier, with high temperatures, increasing the amount of the hot air columns this species needed to take flight, a ground take-off would be possible if there was a downward slope and despite their weight these birds were more agile walker than modern birds, therefore achieving a certain speed that would allow it to fly, the agility of these species could be explained by the need to locate a slope to perform this flight mechanism (Chatterjee, Templin and Junior, 2007)(Alexander,2007).
References
· Alexander, D.E., 2007. Ancient Argentavis Soars Again. Proceedings of the National Academy of Science of the United States of America. 104 (30), pp. 12233-12234
· Chatterjee, S., Templin, R.J., Junior, K.E.C., 2007. The aerodynamics of Argentavis, the worlds largest flying bird from the Miocene of Argentina. Proc Natl Acad Sci U S A.104 (30) pp. 122398-12403