Birds fly north to south to north again, nothing more, in the mesmerizing Oscar-nominated documentary Winged Migration. Yet for some 90 minutes, unadorned reality outdazzles special effects, and poetry-prone viewers may find themselves remembering paeans to nature by Gerard Manley Hopkins. Filmmaker Jacques Perrin, who previously admired the glory of bugs in ''Microcosmos,'' marshaled a brigade of film crews to follow migrations over seven continents, sending cameras up in various winged machines and zooming in close on the ground, too, for extraordinary access to bird behavior. It's a byproduct of human adaptation to a modern, special-effects-assisted movie habitat that one's first reaction to the experience of traveling at eye level with a formation of flapping geese is, this can't be real!
There's no doubting, though, that ''Winged Migration'' is real, in the old-school documentary sense: While Bruno Coulais' New Agey score emphasizes how amazing it is to live in the air, occasional on-screen text provides information on how many thousands of miles various species log each year. Arbitrary gusts of voice-over, meanwhile, narrated in French-accented English by the director -- empty, stilted lyricism about birdie fortitude -- are unnecessary and distracting, especially in a world filled with such wordless marvels of nature.