We determined the stock composition of the juvenile salmon delivered to offspring by a pursuit-diving seabird, the Rhinoceros Auklet (Cerorhinca monocerata) on five breeding colonies in British Columbia, in 2012-2014. We obtained 778 meals (bill-loads) in 11 colony-years, of which 215 (28%) included salmon, and estimated stock composition for 126 pink, 101 sockeye, and 113 chum. The number, species, and stock composition of salmon taken by the birds varied markedly among colonies and years. On the two southernmost colonies there was a dramatic increase in the amount of Fraser River sockeye in diets in 2012, the offspring of the exceptionally large run up the river in 2010. The biennial cycle in pink salmon was also evident: individuals from Puget Sound stocks featured prominently in diets on colonies in 2012 and 2014, but were virtually absent in 2013 and replaced by pinks from more northerly stocks. Salmon generally comprise a minor proportion of Rhinoceros Auklet diets, but our results show that these seabirds will respond to pulses of increased abundance of juvenile salmon.