Suzi Eszterhas / Leopard (Panthera pardus) female stretching, Jao Reserve, Botswana

John Chan / Great horned owl (Bubo virginianus) chicks stretching and flapping their wings, Southern California, USA, May.

John Cancalosi / Great horned owl (Bubo virginianus) chick stretching its wings in nest in a Saguaro (Carnegiea gigantea), is groomed by its parent, Sonoran Desert, Arizona, USA, May.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) chicks aged 20-24 weeks stretching wings, in moult whilst parents fish at sea. Atka Bay, Antarctica. January.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) chick aged six to eight weeks stretching whilst on brooding parent's feet. Adult looking down at chick. Atka Bay, Antarctica. September.

Sven Zacek / Ural owl (Strix uralensis) female stretching wings whilst perched in Spruce (Picea sp) tree. Tartumaa, Southern Estonia. May.

Chase Dekker / Common Loon (Gavia immer) spreading wings, Monterey Bay, California

Ingo Arndt / Upland Goose (Chloephaga picta) male stretching, Torres del Paine National Park, Patagonia, Chile

Donald M. Jones / Common Loon (Gavia immer) stretching, Troy, Montana

Guy Edwardes / Puffin (Fratercula arctica) wings spread backlit, Great Saltee Island, County Wexford, Republic of Ireland, June.

Frederique Olivier / Chinstrap penguin (Pygoscelis antarcticus) adding a stick to its nest and fighting with a neighbouring pair, Aitcho Island, South Shetland Islands.

Peter Bassett / Wandering albatross (Diomedea exulans) chick stretching its wings, Prion Island, South Georgia.