Angelo Gandolfi / Griffon Vultures (Gyps fulvus) soaring at midday on thermals, circling over Vadiello cliffs, Sierra de Guara, Aragon, Spain.

Gerrit Vyn / Lesser Sandhill cranes (Grus canadensis) riding thermals in migration along the Alaska Range near Mt. McKinley. These birds are from the mid-continent population that nest across Northcentral Canada t...

John Downer / Flock of Asian openbill storks (Anastomus oscitans) in flight, soaring in thermals over nesting colony, Thailand.

Donald M. Jones / Turkey Vulture (Cathartes aura) group flying in morning thermals, Sarasota, Florida

Stephen Dalton / Eastern white pelican (Pelecanus onocrotalus) flock soaring on thermals, Europe

Sebastian Kennerknecht / American White Pelican (Pelecanus erythrorhynchos) flock flying, using thermals, Prairie du Chien, Wisconsin

Nick Upton / Migrating Common eurasian cranes (Grus grus) using thermals to gain height over Pyrenees mountains on France / Spain border. November 2008

Richard Du Toit / Cape vulture (Gyps coprotheres) in flight, Giant Castle NP, South Africa

Mike Potts / White pelicans {Pelecanus onocrotalus} soaring in thermals over Danube Delta, Romania

Staffan Widstrand / Short toed / Black crested snake eagle {Circaetus gallicus} and flock of White storks {Ciconia ciconia} flying in the thermals, Serengeti NP, Tanzania, East Africa

DAVID TIPLING / Flock of Dalmatian Pelicans {Pelicanus crispus} circling on thermals, Lake Kerkini, Greece.

Richard Du Toit / Flock of Abdim's storks soaring in sky {Ciconia abdimii} Etosha NP, Namibia

Bryan and Cherry Alexander / Man demonstrating clothing layers (mid layer) at Mount Vinson Base Camp. Vinson Massif, Antarctica, January 2006.

Bryan and Cherry Alexander / Man demonstrates clothing layers (underwear) at Mount Vinson Base Camp. Vinson Massif, Antarctica, January 2006.