These data contain carbon and nitrogen isotope ratios in samples of Black Oystercatcher tissues (feathers and claws), as well as tissues from several species of prey, including mussels, limpets, clams, and snails. Samples were collected across a significant portion of the Black Oystercatcher's range, including the coast of the northern Gulf of Alaska down to the Salish Sea in British Columbia. These data are useful for examining Black Oystercatcher trophic relationships, variation in diet across areas, and relationships of prey selectivity and migration strategies.