Markus Varesvuo / Flock of Griffon vulture (Gyps fulvus) in flight, soaring on thermals, Spain, December

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

Nick Upton / Captive reared juvenile White stork (Ciconia ciconia) flock circling high on thermals soon after release on the Knepp estate, Sussex, UK, August 2019.

Nick Upton / Captive reared juvenile White stork (Ciconia ciconia) flock circling high on thermals soon after release on the Knepp estate, Sussex, UK, August 2019.

Markus Varesvuo / Large flock of Black Kites (Milvus migrans) soaring in thermals, Tarifa, Spain, September

Markus Varesvuo / Flock of White stork (Ciconia ciconia) soaring in thermals, Spain, September

Markus Varesvuo / Flock of White stork (Ciconia ciconia) soaring in thermals, Spain, September

Jeff Vanuga / Dead lodgelpole pines stand in constrast against a winter sun and thermals from Lower Geyser Basin as seen from Fountain Flats. Yellowstone National Park, Wyoming, USA, January 2013.

Eric Baccega / Griffon vultures (Gyps fulvus) soaring on thermals at the Penafalcon (rock housing a colony) in the morning, Salto del Gitano,Monfrague National Park, Unesco Biosphere Reserve, Extremadura, Spain, Dec...

Eric Baccega / Griffon vultures (Gyps fulvus) soaring on thermals at the Penafalcon (rock housing a colony) in the morning, Salto del Gitano,Monfrague National Park, Unesco Biosphere Reserve, Extremadura, Spain, Dec...

Eric Baccega / Griffon vultures (Gyps fulvus) soaring on thermals at the Penafalcon (rock housing a colony), Salto del Gitano, Monfrague National Park, Unesco Biosphere Reserve, Extremadura, Spain, December 2013

Nick Garbutt / Aggregation / flocks of Black Vultures (Coragyps atratus) circling on morning thermals forming over Iguasu Falls, on the Iguasu River, Brazil / Argentina border. Photographed from the Brazilian side o...

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.

Roger Powell / Small flock of Griffon vultures (Gyps fulvus) circling and soaring on thermals, with one Bearded vulture (Gypaetus barbatus) top right. Lamiana, Aragon, Spanish Pyrenees, Spain. May.

Roger Powell / Great white pelicans (Pelecanus onocrotalus) in flock using thermals to fly north on migration, Jordan Valley, Israel, March.

Roger Powell / Great white pelican (Pelecanus onocrotalus) flock using thermals to fly north on migration, Jordan Valley, Israel, March.

Roland Seitre / Egyptian vulture (Neophron percnopterus) flock in flight, circling in thermals, Muscat Governorate, Oman. Endangered.

Roland Seitre / Griffon vulture (Gyps fulvus) flock, soaring high in heat thermals, Catalonia, Spain. March.

Jack Dykinga / California condor (Gymnogyps californianus), saved from extinction, soaring warm thermals. Marble Canyon above the Colorado River, Arizona, USA.