Numerous studies have found that high-density, “traditional” social networks correlate with the use of low-status or local language varieties. Why some people maintain an ancestral language and transmit it to their children, while others abandon it, is a major issue in the study of language endangerment. This study focuses on Guernesiais, the endangered indigenous language of Guernsey, Channel Islands. Baseline data were collected using a questionnaire and semistructured interviews; ethnographic methods then shed light on ideologies, attitudes, and the processes of language shift. Availability of interlocutors correlates strongly with fluency, for both native speakers and learners, but the increasing age and linguistic isolation of many native speakers contributes to both individual and societal language loss, along with other factors. Options for supporting (or reconstituting) social networks through language planning are examined.