Turtles warm themselves by sitting on a tree branch in a park in Bucharest, Romania, on April 29, 2019. (Photo by AP)

Giant male panda Xiao Liwu eats a meal of bamboo at the San Diego Zoo prior to his repatriation to China with his mother Bai Yun, bringing an end to a 23-year-long panda research program in San Diego, California, the US, April 18, 2019. (Photo by Reuters)

Falcons wait to receive medical attention at the Abu Dhabi Falcon Hospital in Abu Dhabi, the United Arab Emirates, on April 28, 2019. (Photo by Reuters)

Palestinian beekeepers collect honey at a farm in Gaza City, Palestine, on April 29, 2019. (Photo by Reuters)

In this April 21, 2019 photo, a cargo ship is seen transiting the Panama Canal on its way to the Atlantic Ocean, while tree trunks that used to be submerged are exposed due to the low water levels of Gatun Lake, Panama. (By AFP)

Fireworks explode over the sky after a welcome dinner organized to commemorate the 30th anniversary of peace-building efforts in Wa State, in Panghsang, Myanmar, on April 16, 2019. (Photo by AFP)

Hare Krishna devotees from all over South Africa sing and chant through North Beach during the 30th annual Rathayatra (Festival of Chariots), in Durban, South Africa, on April 19, 2019. (Photo by AFP)

Japan’s Emperor Akihito (L) walks to the Kashikodokoro imperial sanctuary inside the Imperial Palace to attend a ceremony to report the conduct of his abdication ceremony in Tokyo, Japan, on April 30, 2019. (Photo by AFP)

Central American migrants climb on a train known as "The Beast," continuing their journey toward the United States, in Ixtepec, Mexico, on April 28, 2019. (Photo by Reuters)

Polish teachers demonstrate with placards and balloons in front of the Education Ministry during their strike to call for a 30-percent salary hike in Warsaw, Poland, on April 23, 2019. (Photo by AFP)