Common Loon (Gavia immer) breeding, pre-migratory, and wintering behavior has been well described, but no previous author has characterized failed and non-breeding loon behavior during the summer breeding season. We quantified the summer behavior of non-breeding and failed breeding loons from 15 lakes in Kejimkujik National Park (Nova Scotia, Canada) and the Lepreau watershed (New Brunswick, Canada). Time-activity budgets and event quantifications were used to describe behavioral state and event patterns. The behavior of failed and non-breeders in summer is similar to that described for pre-nesting, pre-migratory, wintering, and breeding loons (except those with young chicks) with foraging the predominant behavior and peering the predominant event. We propose that the behavioral regimen of adult loons is relatively constant throughout the year, with the exception of a two-week period following chick hatching when adults brood their young.