Monitoring to assess spatial and temporal trends in biological diversity is increasingly important as human populations and resource use expands. Most monitoring is carried out by government agencies charged with managing natural resources and by non-governmental organizations (NGOs) with missions to conserve biodiversity. Citizen Science is a venue through which volunteers participate in research, often through data collection over a variety of temporal and spatial scales. Citizen Science operates on the principle that nature enthusiasts of all ages and skill levels can make important, reliable contributions. Citizen Science can be structured to span a range of non-competing goals, from informal public education (i.e., emphasis on “citizen”) to hypothesis-driven research (i.e., emphasis on “science”). As a tool to collect biodiversity data, Citizen Science is a particularly powerful way to monitor across broad geographic and temporal scales. Using Citizen Science for biodiversity monitoring harbors the potential to change public attitudes about science, the environment, and conservation, as active participation in monitoring is an informal education experience. Citizen Science permits the monitoring to be integrated into hypothesis-driven research, promoting an understanding and appreciation of the scientific method and the nature of scientific inquiry. In this paper, we focus on monitoring avian species, yet the tool we describe can be used for any type of biodiversity monitoring.