Walkers cross the river Waalbrug during the first day of the 98th annual four-days walking event, the “Vierdaagse” in Nijmegen, Netherlands, July 15, 2014. The “Nijmeegse Vierdaagse” is an annual public four-day field march which is held since 1909 in the third week of July. (Photo by Erik van 't Wout/EPA)

In this undated photo made available by journal Nature on January 15, 2014, a northern bald ibis (Geronticus eremita) flies in Tuscany, Italy. A new study released Wednesday, January 15, 2014 says the birds choreograph the flapping of their wings, getting a boost from an updraft of air in the wake of the flapping wings by flying behind the first bird and off to the side. When a flock of birds take advantage of these aerodynamics, they form a V. (Photo by Markus Unsöld/AP Photo)

Liu Chunxia, a supporter of Xu Zhiyong, one of China's most prominent rights advocates, is detained by policemen while she gathers with other supporters nearby a court where Xu's trial is being held in Beijing January 22, 2014. When dozens of activists unfurled banners across the country last March and April calling for officials to disclose their assets, they did so at the urging of one of China's most prominent rights advocates, Xu Zhiyong. Xu, 40, stands trial on Wednesday on a charge of “gathering a crowd to disturb public order” punishable by up to five years in prison. His case will almost certainly spark fresh criticism from Western governments over Beijing's crackdown on dissent. (Photo by Kim Kyung-Hoon/Reuters)

People watch dragon dance performance in front of a business establishment in celebration of Chinese New Year at Manila's Chinatown district of Binondo, Philippines, Friday, January 31, 2014. (Photo by Bullit Marquez/AP Photo)

Sri Lankan military personnel march during the country's 66th Independence Day celebrations in the central town of Kegalle, about 40 kms from the capital Colombo on February 4, 2014. Sri Lanka cemmemorates its independence from British rule on February 4, 1948. (Photo by Ishara S. Kodikara/AFP Photo)

A member of the mainly Christian “anti-balaka” (anti-machete) militia trains in the Boeing neighbourhood of Bangui, Central African Republic, on February 24, 2014. (Photo by Fred Dufour/AFP Photo)

A woman and a child walk past the remains of collapsed houses damaged during the April 2015 earthquake, in Bhaktapur, Nepal March 18, 2016. The two devastating earthquakes that struck Nepal last year killed almost 9,000 people across the country. Inside the Kathmandu Valley almost 2,000 died, and some of the area's most important cultural and heritage sites were completely destroyed. As Kathmandu inhabitants prepare to mark the one-year anniversary of the event, thousands are still displaced and millions are living in temporary shelters. (Photo by Navesh Chitrakar/Reuters)

Ryan Randall plays the bagpipes outside a polling station in Edinburgh, Scotland September 18, 2014. Polling in the referendum on Scottish independence began on Thursday morning, as Scotland votes whether or not to end the 307-year-old union with the rest of the United Kingdom. (Photo by Paul Hackett/Reuters)