In December 1956 a young American ornithologist, Chandler Robbins, put a metal band on the leg of a nesting Laysan albatross on Midway Atoll. Albatrosses don’t breed until they are about five, so she was at least that old already. Around 2002 he went back to Midway, noticed a worn band that needed replacing, read the number, and found it was one of his. Biologists then thought the species lived about forty years. She is now called Wisdom, and she has kept coming back to Midway to nest well into her seventies, wearing through band after band. Robbins died in 2017, at ninety-eight. So the record of how old she is has been written on things that wear out, by a man who was a young bird-bander when it started, and so far she has outlasted the bands and him too. Her age is only a lower bound: all anyone knows is the year somebody started counting.