Abstract. To facilitate communication and the exchange of information between patients, nurses, lab technicians, health insurers, physicians, policy makers, and existing knowledge-based systems, a set of shared standard terminologies and controlled vocabularies are necessary. In modern health information management systems, these vocabularies are defined within formal representations called ontologies, where terminologies are only meaningful once linked to a descriptive dataset. When the datasets and their conveyed knowledge are changed, the ontological structure is altered accordingly. Despite the importance of this topic, the problem of managing evolving ontological structures is inadequately addressed by available tools and algorithms, partly because handling ontological change is not a purely computational affair. In this paper, we propose a framework inspired by a social activity, birdwatching. Using this model, the evolving ontological structures can be monitored and analyzed bas...