Members of Germany's elite police unit, the Spezialeinsatzkommando, or SEK, demonstrate an abseil deployment from a helicopter during a media event on March 20, 2012 in Minden, Germany. The SEK is the special response team of Germany's state police force and typically deploys in high-risk situations, such as bank robberies, hostage takings and the arrest of armed and dangerous fugitives. (Photo by Thomas Starke/Getty Images)

An climber ascends a silo covered in ice in Cedar Falls, Iowa, United States, January 17, 2016. The owners have connected hoses to the top of the silo and spray it with water in winter months to freeze the exterior for climbing. (Photo by Jim Young/Reuters)

Amateur honorable mention | Common raven at Banff National Park in Alberta, Canada. (Photo by Colleen Gara/Audubon Photography Awards)

A bomb-laden Su-25 jet at the Hmeimim air base in December 2015. Russia's lease agreement obliged Assad’s military to safeguard the perimeter of the Hmeimim base, while giving Moscow legal jurisdiction over the facilities inside. Negotiating perimeter protection from Syria’s new rulers will be vital for the Russian bases in an era of wire-controlled drones immune to jamming. (Photo by AP Photo)

The Spanish photographer Xavi Bou digitally combines sequential pictures of birds to create a single image, or chronophotograph, that reveals the shapes of their flight paths against Catalonian skies. His work shows the variety and beauty to be found in the daily activities of the local birds, including spiralling storks, swooping starlings and giddy swifts. Here: European herring gulls at Llobregat Delta. (Photo by Xavi Bou/Rex Features/Shutterstock)

A juvenile specimen of the recently-discovered Australian Peacock spider, Maratus Albus, sits on the nib of a pencil in this undated picture taken in Western Australia's Nuytsland Nature Reserve. (Photo by Jurgen Otto/Reuters)