The human residents of cities represent a largely untapped and potentially vast source of information about urban wildlife. One simple and scientifically valuable contribution involves the reporting of sightings of tagged animals, but even in urban areas, such reports are relatively rare. We draw on two case studies of conspicuously tagged and iconic animals to consider human reactions to wildlife tags, and how these influence the likelihood of unsolicited reports. We evaluate potential strategies for increasing participation from this pool of potential citizen scientists and maximising the reliability of these contributions. In both studies, public reports contributed substantial and largely accurate data. We conclude that such reports are often of unique value, and that common sources of reporting error can be minimised by careful tag design and clear advice to participants. Effective information campaigns can have unexpected effects on reporting rates, but in general, communication is crucial to raising awareness and encouraging public involvement. New interactive web-based tools have the potential to dramatically increase public accessibility to information and encourage involvement by providing instant feedback, access to research updates, and encouraging the formation of clusters of citizen scientists.