At Punta San Juan, Peru, we examined the foraging behaviour of three Humboldt Penguins Spheniscus humboldti following breeding failure, and we compared that behaviour with the behaviour of 22 breeding birds with chicks. Failed breeders appear to take longer foraging trips, to make deeper and longer dives and to dive less often per hour at sea than breeding birds do. We suggest that failed breeders either take longer foraging trips to reduce the number of trips they make to the colony, which reduces the costs of transit, or they travel to more distant foraging areas, as documented for Chile. Study of non-breeding birds that have successfully fledged young would help to clarify the differences in foraging behaviour between non-breeding and breeding birds.