Paris Jackson arrives at the Calvin Klein Collection fashion show during New York Fashion Week at New York Stock Exchange on February 13, 2018. (Photo by Ouzounova/Splash News and Pictures)

Artist German Vinogradov acts in the performance of the burning of installation, devoted to Maslenitsa, or Pancake Week, a pagan holiday marking the end of winter, in the village of Nikola-Lenivets, Kaluga region, Russia, February 17, 2018. (Photo by Maxim Shemetov/Reuters)

A demonstrator shows her arm with the name “Marielle” written on it, as she performs during a protest against the murder of councilwoman Marielle Franco in Rio de Janeiro, Brazil, Tuesday, March 20, 2018. Franco's murder came just a month after the government put the military in charge of security in Rio, which is experiencing a sharp spike in violence less than two years after hosting the 2016 Summer Olympics. (Photo by Leo Correa/AP Photo)

South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)

Yuri Gagarin does not always show up in full-scale astronautics. In this picture he smiles during his summer vacation in Sochi, Russia in 1961 with sunglasses and sunhat in the camera. (Photo by Imago/Eastnews)

Children in a Hong Kong refugee resettlement area watch as former Vice President Richard Nixon shows them his badminton service. Nixon visited Hong Kong, April 4, 1964, during his tour of countries in the Far East. (Photo by AP Photo)

A rickshaw puller transports passengers through a water-logged street after heavy rain in Kolkata, India on June 26, 2018. (Photo by Rupak De Chowdhuri/Reuters)

Bloodthirsty by Thomas P. Peschak, Germany/South Africa — winner, Behaviour: birds. When rations run short on Wolf Island, in the remote northern Galápagos, the sharp-beaked ground finches become vampires. Their sitting targets are Nazca boobies and other large birds. The finches rely on a scant diet of seeds and insects, which regularly dries up, so they drink blood to survive. ‘I’ve seen more than half a dozen finches drinking from a single Nazca booby,’ says Tom. Rather than leave their nests the boobies tolerate the vampires, and the blood loss doesn’t seem to cause permanent harm. (Photo by Thomas P. Peschak/2018 Wildlife Photographer of the Year)