“Cassowaries are large, flightless birds related to emus and (more distantly) to ostriches, rheas, and kiwis”, writes Olivia Judson in the September issue of National Geographic magazine. How large? People-size: Adult males stand well over five foot five and top 110 pounds. Females are even taller, and can weigh more than 160 pounds. Dangerous when roused, they’re shy and peaceable when left alone. But even birds this big and tough are prey to habitat loss. The dense New Guinea and Australia rain forests where they live have dwindled. Today cassowaries might number 1,500 to 2,000. And because they help shape those same forests – by moving seeds from one place to another – “if they vanish”, Judson writes, “the structure of the forest would gradually change” too. (Photo by Christian Ziegler/National Geographic)

Two carnival revellers masquerade as Leonardo da Vinci's painting “Mona Lisa” pose in St. Mark's Square in Venice, Italy, Sunday, January 31, 2016. Carnival-goers in Venice are being asked by police to momentarily lift their masks as part of new anti-terrorism measures for the annual festivities. (Photo by Domenico Stinellis/AP Photo)

U.S. Marine Lt. Ben Reid from 1/2 Charlie Company of Task Force Tarawa waits to be medivaced after being hit with shrapnel and a machine gun round, in the southern Iraqi city of Nasiriyah, on March 23, 2003. The Marines suffered a number of deaths and casualties during gun battles throughout the city. (Photo by Joe Raedle via The Atlantic)