In 2015, Harold Greeney trained his camera on a mourning dove nest stitched into the crook of a cactus. As an ornithologist, Greeney studies the love lives of birds—cooperative breeding in nightingale-thrushes, parenting strategies of spotted barbtails, breeding biology in speckled hummingbirds, you name it. His goal today was to capture the breeding habits of doves in an urban setting. Instead, he captured perhaps the most horrifying bird-on-bird behavior the world has ever seen...

Greeney has a possible explanation as to what’s happening—but it probably won't make you feel any better. When Gila woodpeckers get thirsty, he speculates, they crack open a couple of nestling heads like you or I might open a six-pack.