The hummingbird Susan Heath is banding weighs 3.06 grams—an amount, I will learn, when she places a bird on my open palm, is too light for a human hand to even feel. Ten minutes earlier, the bird flew into a nearby trap, a feeder cloaked in a net with a single opening, at the Nature Conservancy’s Davis Mountains Preserve, in West Texas. Now Heath is collecting its measurements and giving it the leg band it will wear for the rest of its life, in the name of science.

This overcast August morning marks the second day of the biennial Davis Mountains Hummingbird Celebration. As a dozen onlookers surround her table, Heath talks through the identification process. The bird’s plumage is not bright green or rufous, a warm rust color, which rules out several species. This is either a black-chin

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