Many birds that are territorial in the breeding season live in groups during the nonbreeding season, thereby gaining benefits such as protection from predators and increased access to resources. However, how the social connections in group life change across seasons in migratory animals is mostly unknown. We ask whether winter social connections continue during the breeding season in a migratory songbird. Golden-crowned Sparrows (Zonotrichia atricapilla) have distinct, stable winter communities that include both site and group fidelity across years: birds almost always rejoin the same social community each year after migration. If these birds have social connectivity across migration, we would expect individuals that associate in winter would also associate together on their breeding grounds. Our small-scale GPS tagging study combined with intensive social behavior data indicates that sparrows in the same tightly knit winter community migrate to highly disparate locations during summer, and therefore, social connections in winter do not continue in summer. This suggests that Golden-crowned Sparrows have entirely separate social structures across seasons and that long-term social memory allows them to reform stable groups each winter.