Most seabirds delay reproduction for multiple years. The standing hypothesis is that seabirds delay reproduction while they develop foraging skills. Here, I clarify an old but understudied alternative hypothesis: young seabirds also undergo a phase of social development before beginning reproduction. I then provide a prefatory, but necessary, test of this hypothesis with American Herring Gulls (Larus argentatus smithsonianus), asking whether young gulls have an opportunity for social development at colonies before breeding. A corresponding set of predictions is that young gulls are (A) present at breeding colonies, (B) socially engaged, and (C) not breeding. I conducted census counts and behavioral observations at a northwest Atlantic breeding colony on Kent Island, New Brunswick, Canada during summers 2022–3, along with supplementary observations at Great Duck Island, Maine, USA. Immature gulls in an advanced predefinitive plumage stage were common (2.5–6.2% of a total census of ∼4,000 birds). Younger birds, identified via less-advanced predefinitive plumage stages, were nearly absent (generally <1% of census). Immature birds were socially engaged around foreign territories. Yet only 1–4 immature birds held territories or nests of their own. This phenomenon suggests the social conditions at breeding colonies may set the stage for forms of social development that, in turn, set the stage for life history and plumage evolution.