The Spanish photographer Xavi Bou digitally combines sequential pictures of birds to create a single image, or chronophotograph, that reveals the shapes of their flight paths against Catalonian skies. His work shows the variety and beauty to be found in the daily activities of the local birds, including spiralling storks, swooping starlings and giddy swifts. Here: European herring gulls at Llobregat Delta. (Photo by Xavi Bou/Rex Features/Shutterstock)

This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

Migrants ride on top of a northern bound train toward the US-Mexico border in Juchitan, southern Mexico, Monday, April 29, 2013. Migrants crossing Mexico to get to the U.S. have increasingly become targets of criminal gangs who kidnap them to obtain ransom money. (Photo by Eduardo Verdugo/AP Photo)

A pack of wild smooth-coated otters, nicknamed the “Zouk family”, crosses Penang Road in Singapore on March 3, 2021, the World Wildlife Day. The “Zouks”, a well-known otter family in Singapore, started out from the Istana on Wednesday, and made a “royal” tour of various landmarks in Singapore. (Photo by Chine Nouvelle/SIPA Press/Rex Features/Shutterstock)

Two men pull their boat over a railroad crossing in Nidderau-Eichen near Frankfurt, Germany, Friday, January 13, 2023. They came over the fields that were flooded by heavy rainfalls and continued their trip on the other side. (Photo by Michael Probst/AP Photo)

Peter Carberry riding Gabbys Cross falls off during the Randox Grand National Chase during day three of the Randox Grand National Festival at Aintree Racecourse on April 15, 2023 in Liverpool, England. (Photo by Michael Steele/Getty Images)

Jubilee Class steam locomotive 45596 Bahamas crosses the Forth Bridge on its way from Edinburgh Waverley to Aberdeen on a day trip operated by The Railway Touring Company on Wednesday, April 19, 2023. (Photo by Jane Barlow/PA Images via Getty Images)

An activist shouts amid clashes with Lebanese riot police during a protest to demand the opening of Rafah border crossing between Egypt and the Gaza Strip, outside of the Egyptian embassy in Beirut, Lebanon, 22 February 2024. (Photo by Wael Hamzeh/EPA/EFE)