Despite their massive size Andean condors can remain aloft for hours while expending little energy (Pedro Szekely / CC BY-SA-2.0/Creativecommons.org)

Andean Condors, which weigh between 20 to 30 pounds (9 to 13 kilograms) and boast a wingspan of more than 10 feet, are one of the world's heaviest and largest flying birds. Yet the majestic vultures, which spend their days circling the Andes mountains and nearby Pacific coasts of western South America in search of carcasses, manage to stay afloat for hours.