Describing an ephemeral phenomenon, a passing fancy, a fad. Originally this expression referred to the relatively brief span of a human life. It was recorded by numerous writers and was included in James Kelly’s Scottish Proverbs of 1721. By the nineteenth century it had become a less serious thought. T. C. Haliburton (Sam Slick) included it in Wise Saws (1843): “I am a bird of passage—here today and gone tomorrow.”