Of all bird architects, the Baltimore Oriole seems most aware that form follows function and that bird nests are for birds. Her classic pendulous nest is formed with sensitive engineering and flawless weaving. It's the Nest of the Year, year after year. On a warp of flexible bark fibers attached to the tips of high branches, she looms a bag of grass, horsehair and string. And when the wind blows, the cradle does rock.