The purpose of this study is to examine the potential of social networking sites for autonomous language learners, specifically the role of hashtag literacies in learners' affiliation performances with native speakers. Informed by ecological approach and guided by Zappavigna's (2012) concepts of "searchable talk" and "ambient affiliation", the current study employs an autoethnographic approach by analyzing the researcher's own Twitter experiences in his target language, Spanish, over the period of a year. The participant's journal, tweets and conversations, and both qualitative and quantitative analysis of the hashtags accompanying tweets show that Twitter has potential to create a space for autonomous learners to enrich their language learning experiences. The thematic analysis of the data further reveals that hashtags, which perform an affiliative function, enable the learner to bond around particular values within authentic discourse communities in his target language. The methodological and practical outcomes of this longitudinal study for second language learning and teaching contexts are also discussed.