The Great Backyard Bird Count (GBBC) is a late winter weekend survey of bird populations across the United States and Canada. Developed by the Cornell Lab of Ornithology and Audubon, the GBBC engages tens of thousands of participants. Data is collected with postal code or town geographical resolution. Started in 1998, the GBBC provides a place-based characterization of a given area through a checklist of birds observed at that location. Presently, GBBC collects approximately 50 thousand checklists annually during a 4-day period in mid-February.