When a male ruby humming bird turns to the sun, its dark plumage flashes a bright color.

In pursuit of the world’s smallest bird, we’ve come to the backyard of a flamingo pink house in Palpite, Cuba. Ornithologist Christopher Clark has a car full of gear to unload: cameras, sound equipment, a sheer cube-shaped cage. Within minutes of arriving this May morning, Clark is spinning around in circles. He’s trying to follow the path of a bullet with wings as it whizzes from one clump of orange fire bush blossoms to the next. When the hummingbird pauses to draw sugary fuel from the flowers, his wings continue to beat a grayish blur too fast for the human eye to resolve.

Even by the Lilliputian standards of hummingbirds, Cuba’s bee hummingbird (Mellisuga helenae) is a midget—literally the smallest bird in the world. Its iridescent green body weighs a bit more than the average almond. Locally it’s known as zunzuncito—the little buzz-buzz, after the sound it makes—and is even smaller than its cousin the zunzun, or emerald hummingbird.