A Polisario fighter sits on a rock at a forward base on the outskirts of Tifariti, Western Sahara, September 9, 2016. At a rocky outpost in Western Sahara, a new generation of soldiers who have never known war are mobilising as tensions resurface in one of Africa's oldest disputes after a quarter century of uneasy peace. (Photo by Zohra Bensemra/Reuters)

Two Czech Gripen fighter planes demonstrate a flight interception of a Belgian air force transport plane over the Czech Republic, as part of NATO drills on September 12, 2018. (Photo by Francois Lenoir/Reuters)

A golden pheasant is seen at Hangzhou Safari Park in Hangzhou, Zhejiang Province, China, November 13, 2016. According to local media, the pheasant gains popularity as its golden feathers resemble the hairstyle of U.S. President-elect Donald Trump. (Photo by Reuters/Stringer)

An undated handout picture made available by the Symbio Wildlife Park on 28 November 2016 shows three Pygmy Marmoset monkeys including an adult male, a female juvenile and a four-week-old baby, at the Symbio Wildlife Park in Helensburgh, South of Sydney, New South Wales, Australia. (Photo by EPA/Symbio Wildlife Park)

Mercury and Maia, fueled and overhauled, are waiting in the Tay at Dundee, for favorable weather to start the flight to the Cape, a distance of 6,370 miles. The composite machine moored in the Tay River, at Dundee, on September 23, 1938. (Photo by AP Photo)

A saddle-billed stork stands in the grassland at the Nairobi National Park near Nairobi, Kenya January 23, 2017. (Photo by Thomas Mukoya/Reuters)

South Korea's Black Eagles aerobatics team performs an aerial display forming a Ying and Yang logo during the Singapore Airshow at Changi exhibition center in Singapore on February 16, 2016. (Photo by Roslan Rahman/AFP Photo)

A sofa floats in the polluted waters of Jacarepagua Lagoon, during a press tour in Rio de Janeiro, March 9, 2015. A press tour was organised by biologist Mario Moscatelli, to call attention to pollution on the waters of the lagoons which surround the Rio 2016 Olympic Park. (Photo by Ricardo Moraes/Reuters)