Bird Cloud is the name Annie Proulx gave to 640 acres of Wyoming wetlands and prairie and four-hundred-foot cliffs plunging down to the North Platte River. On the day she first visited, a cloud in the shape of a bird hung in the evening sky. Proulx also saw pelicans, bald eagles, golden eagles, great blue herons, ravens, scores of bluebirds, harriers, kestrels, elk, deer and a dozen antelope. She fell in love with the land, then owned by the Nature Conservancy, and she knew what she wanted to build on it a house in harmony with her work, her appetites and her character, a library surrounded by bedrooms and a kitchen.