Brian Doyle's essay "Joyas Voladoras" contemplates the hummingbird's extraordinary physiology—its pencil-eraser-sized heart beating ten times per second—and contrasts it with the blue whale's seven-ton heart. The piece explores how all creatures have roughly two billion heartbeats to spend in a lifetime, spending them slowly like a tortoise or fast like a hummingbird, reflecting on the price of metabolic ambition and the mysterious lives of Earth's most extreme creatures.