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)

A visitor holds an Israeli-made rifle during the 8th International Land and Naval Defense system exhibition, in New Delhi, India, on February 6, 2014. (Photo by Anindito Mukherjee/Reuters)

Ukrainian state emblem is seen on a gun's holster as soldiers guard naval base in the village of Novoozernoye, some 91 km west of Crimean capital Simferopol, Ukraine, on Monday, March 3, 2014. Ukraine says Russian forces controlling the strategic region of Crimea are demanding that the crew of two Ukrainian warships in Sevastopol's harbor must surrender. (Photo by Ivan Sekretarev/AP Photo)

People walk through crop circles in a cornfield near Raisting, Germany, on July 28, 2014. According to media reports, a balloonist had discovered the circle some days ago. Since then, hundreds of people came to the field to watch it, however it is unclear who did create the pattern. (Photo by Karl-Josef Hildenbrand/DPA)

Two men ride a motorcycle away from a fire in Athens on Friday, July 17, 2015. Greek firefighters battled large brush and forest fires on the outskirts of Athens and in the country's southern Peloponnese region Friday, where flames forced the evacuation of at least three villages and two summer camps. (Photo by Giorgos Bamboukos/InTime News via AP Photo)

A six-year-old acrobat performs on the opening of a tourist festival in Bozhou, Anhui province, China May 3, 2015. (Photo by Reuters/China Daily)

Russian Tu-95MS strategic bombers fly in formation during rehearsals for the Victory Day military parade, with St. Basil's Cathedral seen in the foreground, in central Moscow May 5, 2015. Russia will celebrate the 70th anniversary of the victory over Nazi Germany in World War Two on May 9. (Photo by Tatyana Makeyeva/Reuters)

A young fan cheers while waiting for the ticker tape parade to celebrate the U.S. women's soccer team World Cup victory, Friday, July 10, 2015, in New York. The World Cup winning U.S. women's football team rolled up New York City's “Canyon of Heroes” on Friday, with a blizzard of confetti swirling overhead in the first ticker-tape parade honouring a women's sports team. (Photo by Adam Hunger/AP Photo)