This was Ana Gathreaux’s first overnight of the year. Since her husband was away at an ornithological conference, she had decided to camp out in the lab; there was no point returning to the empty loft at night only to drag herself back to work before dawn. She’d keep bird hours for two weeks, or as long as her sparrows’ zugunruhe—their restlessness—lasted.

Ana had spent half the night in an absurdly uncomfortable lawn chair, and rising now, she wasn’t quite sure she’d last the full two weeks in the lab. Her lower back ached. Her legs were stiff. She stretched her arms above her head in the red-gelled light. Her hair had come loose and she gathered it behind, grabbed a clip from her belt loop—she always kept one there—and clipped it on top of her skull. The previous night had been perfect for migration. The Doppler images on her computer showed ideal conditions over Manhattan and the entire Northeast: there’d been a cold front, a gibbous moon. On the computer she’d even watched the density of birds gathering over Long Island and Jamaica Bay. They appeared as green specks, ghostly, fleeting, a mineral flame. Later, she’d estimate the density of migrants on the screen and compare that with the behavior of her caged sparrows in the lab. Was there any correlation between the two? Caged for six months in a lightless room in the middle of Manhattan—with no sun or moon or stars to steer by—how did her sparrows know it had been a perfect night to migrate to the south?

Ana recorded the time of her birds’ waking: 5:04 a.m. Then she approached the cages. They were bathed constantly in the dim glow of a photographic safe light, but the birds seemed to have grown accustomed to the odd illumination. They hopped in their cages, twitched their wings. She opened one of the wire doors, reached in, cupped a sparrow, and brought him fluttering from the cage.

Good morning, she whispered.

He flapped his wings, tried to fly, but she held him fast by his legs between her fingers. He was a male, a first-year fledge. A small, grayish bird with a yellow wash around his eyes. Passerculus sandwichensis. A rather unglamorous bird, yet good in the lab. Easy to rear. They grew on you.