Argentavis: Prehistoric Animal of the Week

It is International Vulture Awareness Day this week!  In honor of this I shall be going over a prehistoric vulture (probably) of epic proportions!  Check out Argentavis magnificens!  Argentavis was the largest flying bird of all time.  It is only known from fragmentary remains including part of the beak and the wing but the humerus (upper arm bone) alone from the wing is almost the length of an entire adult human arm!  It lived during the Miocene era about 6 million years ago in what is now South America and its name translates to "Magnificent Argentina Bird".

Argentavis life reconstruction by Christopher DiPiazza.

To put into perspective how massive this bird really was lets look at the largest flying birds of today.  There is the Wandering Albatross (Diomedea exolans) with a wingspan of twelve feet but this is mostly wings.  The bird itself isn't really that large.  Then there is the Andean Condor (Vultur gryphus) which is quite large with a wingspan of about ten feet and a body length of about four feet from beak to tail.  There are two of these guys at the zoo I work at and they are quite intimidating when being viewed up close.  It looks like a child wearing a scary bird costume... but it's a real bird.  Argentavis would have dwarfed both of these birds.  Judging by the arm bones found, Argentavis is estimated to have had a wingspan of over twenty feet and its body would have been the size of a man's at about six feet tall!  That is a HUGE bird.

Andean Condor

Judging by the parts of the skull found it is believed by many that Argentavis was some sort of a vulture but it is possible it could have been something more similar to a huge eagle as well.  Then again there are some birds today that sort of blur those lines anyway like the Bearded Vulture (Gypaetus barbatus) or Egyptian Vulture (Neophron percnopterus).  They both have "vulture" in their names but they are somewhat genetically separated from the the birds that we typically consider "vultures", hovering (or should I say soaring?  BAM) somewhere between vulture and eagle/hawk on the family tree.

Argenativis skeleton mount reconstruction.

So how did a bird this big fly?  Its wings must have been vast enough to make the wing to weight ratio steep enough combined with special adaptations that all flying birds possess like air sacs, hollow bones and rigid feathers (the first two not originally intended for flight we know thanks to their presence in non-avian dinosaurs).  Also keep in mind that Argentavis was only the largest flying bird of all time.  Some pterosaurs had wingspans about the same as small airplanes and were the size of giraffes when standing on the ground!

It is likely that Argentavis would have done very little flapping with its wings while in the air.  Just take a look at the largest flying birds today and you will find that all of them soar and glide, relying on thermals to gain altitude.  The bigger a bird's wings are, the more work it is to flap them.  This being said it is also difficult for a large flying bird to take off.  This is why many of them, like condors, prefer to perch and nest on the sides of cliffs and canyons so all they need to do in order to get airborne is jump off!  Taking off from flat ground can be a daunting task that requires a lot of running space to finally get in the air (think how long it takes for an airplane to get in the air from the runway).  Now imagine a bird the size of Argentavis trying to get off the ground!  It must have been quite a site!

Thats all for this week!  Go to your local zoos and check out some of the modern vultures for yourself!  As always feel free to comment below or on our facebook page!  

References

Campbell, Kenneth E. Jr. & Tonni, E.P. (1983). "Size and locomotion in teratorns". Auk 100 (2): 390–403.

Chatterjee, S.; Templin, R. J.; Campbell, K. E. (2007-07-24). "The aerodynamics of Argentavis, the world's largest flying bird from the Miocene of Argentina". PNAS 104 (30): 12398–12403. doi:10.1073/pnas.0702040104. PMC 1906724. PMID 17609382