Citizen science is the public participation in scientific research by gathering, submitting or analyzing data (Bonney et al., 2016). It allows saving time and money; and bridge the intellectual divide between formal science and people (Skarlatidou et al., 2019). However, the knowledge generation processes and the legitimacy of the knowledge generated through citizen science has been a concern (Bonney et al., 2014). In this paper, we explore the legitimacy issue through the lens of Mansell's (2013) framework through 2 detailed case studies from Turkey in the field of ornithology. Mansell provides a typology of knowledge systems with respect to authority as constituted or adaptive; and nature of knowledge as curated or ephemeral (Mansell, 2013). She highlights constituted authority as in formal science institution, and adaptive authority that relies on bottom-up knowledge generation processes. Regarding knowledge, she defines curated knowledge as long-term accumulated knowledge, and ephemeral knowledge for more immediate action (Mansell, 2013). This categorization allows for examining the transitions between traditional and non-traditional knowledge generation mechanisms, address the legitimacy concern and demonstrate how they coevolve to form social imaginaries. The case studies exhibit a deeper understanding of how knowledge is generated, shared and diffused; the critical actors and their relations that play a role in its legitimization, how these processes depend on the authority and nature of knowledge, as well as the motivations of participants. The results will be supplemented by preliminary results from a large survey among users and non-users of these platforms.