Animalof the Week -- July 9, 2007

I worry that I am starting to sound a bit like a countryside diary of late, what with my tales of cockchafers, pigeons, swifts, and other things that I see as I pootle around London, such as piranhas and golden moles. So this week I am going to resist the temptation to regale you with the tale of peregrine falcons spotted over Clapham on Sunday morning.

Instead, this week's AOTW is something a slightly larger and much rarer bird of prey. Rarer to the extent of being extinct, for about 6 million years. This week's Animal of the Week is Argentavis magificens (giant teratorn). This relative of the living condors was the largest flying bird ever to have lived. With a wingspan of up to 8 m (28 feet) and weighing possibly as much as 100 kg (220 lb). For reference, a wandering albatross has a wingspan of 3.83 m, modern day Andean condors have a wingspan of 3 m and weigh up to 12 kg, and the heaviest flying birds, European (AOTW, April 11, 2005) and Kori bustards weigh no more than 20 kg.

The teratorns were large birds of North and South America that lived from the Miocene to the Pleistocene (15 million to 11 thousand years ago), and this species survived in Argentina from 8–6 million years ago. Other teratorns were not much larger than the modern-day condors, but Argentavis magnificens was truly a monster. People have speculated whether and how such an enormous bird could fly, but the imprints of feather attachments on the birds wing bones (an upper-arm bone would have been the same length as a whole human arm) show that they had flight feathers. Fortunately, the lack of the Andes in South America at the time these birds lived meant that strong westerly winds whipped across the continent, which would have helped the bird take to the sky with a little running around and flapping.

Whether these birds scavenged or hunted is also a bone of contention. Other teratorns almost certainly hunted, because they resembled eagles, which hunt, much more than they did their close relatives condors, which scavenge. But could a bird this size be an active hunter? Perhaps it did a little of both, driving the marsupial lions away from their kills of giant sloths or weird camels with trunks (South America was different then) when the opportunity arose, and when it didn't, swooping down on animals up to the size of hares and small dogs, picking them off the ground, and swallowing them whole.

This week's image may not be entirely accurate. Certainly Argentavis magnificens would never have soared over the heads of Japanese cartoon characters, or any humanoids for that matter. Furthermore, the head may not have been bald. But there you go, needs must when you need to steal a picture.

What a bird!