And then there is the albatross. Perhaps the most heartbreaking mobile romance of all. An albatross may spend two or three years at sea without touching land. When it does return to its breeding colony—say, on South Georgia Island or Midway Atoll—it must find its mate again among thousands of identical birds. They recognize each other not by sight, but by an elaborate, choreographed dance of clacking beaks and skyward faces. If one fails to return from the long wandering—if it drowns, or is hooked by a longline, or simply disappears into the endless swell—the other will return year after year, dancing alone for a ghost. Biologists call this “site fidelity.” Poets would call it grief.