The Giant Teratorn (Argentavis magnificens)

The largest flying bird known to science was the giant teratorn, an extinct condor that lived in South America during the Miocene over 5 million years ago.  It had a wingspan of 21 feet and weighed an astonishing 155 pounds.  It inhabited the Andean Mountains and dry flat pampas, but fossils from this era are rare, and we don’t really know the full extent of its range.  A bird of this size likely had a long lifespan of 50-100 years.  Scientists disagree about its dietary habits.  Some think it was an active predator, swallowing relatively small prey whole because its beak was not built for tearing open large carcasses with tough hides.  However, others believe it was mostly a scavenger because a bird of this size would require 20 pounds of meat per day, and it’s unlikely consuming small animals could satisfy this appetite.  I agree with the latter speculation, though the teratorn may have ingested small animals, if given the opportunity.  It was related to storks and New World vultures, both of which are opportunistic feeders.

Size comparison between the largest flying bird known to science and a school bus.

Specimens of the giant teratorn are only known from 4 localities in South America.  Scientists are interested in figuring out how such a large heavy bird could fly, but the amount of fossil material available from this species is meager, making it difficult to determine this from the few bones they have.  Happily for them, there is abundant fossil material of the closely related North American teratorn–Teratornis merriami. Over 100 specimens of this late Pleistocene species have been excavated from the Rancho la brea tar pits in California.  Additional fossil specimens of North American teratorns have been found in Arizona, Nevada, Florida, and New York.  It had a continent wide distribution but probably occurred in low numbers–a slow breeding yet long-lived species.  T. merriami had a wingspan of 11 feet, less than that of its South American cousin, but still impressive.  Nevertheless, the similarity in anatomy between the 2 species allowed scientists to use specimens of T. merriami to determine how the giant teratorn could fly.  Scientists think it had to run downhill against the wind to get airborne.  Then, it could ride rising warm air (thermals) to get high in the sky where it searched for carrion. It was more of a glider than a flyer.  Just a slight slope in the land would have been adequate for a teratorn to get airborne.  Thermals can occur in a very small space, and teratorns could circle inside these quite narrow thermals to attain height.

 

 

 

Fig. 4.

Diagram from paper referenced below (Chatterjee 2007) showing how the giant terratorn took off and landed.

No extant species of flying birds approach the wingspan and weight of the giant teratorn, but some are almost as big as the late Pleistocene Merriam’s teratorn.  The kari bustard (Ardeotis tardi), a kind of crane, reaches 40 pounds.  The largest turkey (Maleagris gallopavo) ever killed by a hunter weighed 37 pounds.  Dalmatian pelicans (Pelecanus crispus) are heavy flying birds.  The greater albatross (Diomedea exulans) has a wingspan of 11 feet.  This species gets airborne by running into the wind downslope from the top of waves, much like the extinct teratorns.  The Andean condor (Vultur gryphus) is the most similar living species to the teratorn.  They are closely related and likely occupy a similar ecological niche.

Andean condor in front of an Homo sapiens.

Video of the extant bird with the longest wingspan–a great albatross.  Note the difficulty they have with take off.

References:

Chatterjee, S.; and R. J. Templin, and K.E. Campbell

“The Aerodynamics of Argentavis; the World’s Largest Flying Bird from the Miocene of Argentina”

PNAS 104 (30) 2007

Palmqvist, Paul; and Sergio Vizcaino

“Ecological and Reproductive Constraints of Body Size in the Gigantic Argentavis magnificens (Aves: Teratornighidae) from the Miocene of Argentina”

Ameghiniana 40 2003

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