Each February, for four days, the world comes together for the love of birds. Over these four days we invite people to spend time in their favorite places watching and counting as many birds as they can find and reporting them to us. These observations help scientists better understand global bird populations before one of their annual migrations. Launched in 1998 by the Cornell Lab of Ornithology and National Audubon Society, the Great Backyard Bird Count (GBBC) was the first online participatory-science project (also referred to as community science or citizen science) to collect data on wild birds and to display results in near real time. Birds Canada joined the project in 2009 to provide an expanded capacity to support participation in Canada. In 2013, we became a global project when we began entering data into eBird, the world’s largest biodiversity-related participatory science (community science or citizen science) project.