Welcome to the Winter Atlas!
Winter is a critical time of year for bird populations because food and cover can be limiting, and severe winter weather events can result in high mortality. Additionally, the breeding productivity of birds can be affected by their health and condition coming out of the previous winter season. Increasingly, it is known that those bird species which winter in North America are also facing rapidly changing environments due to land use change and climate change. Yet winter bird distribution and abundance remain much less extensively studied than do those in the breeding season. Pennsylvania’s first Winter Atlas, as part of the 3rd Pennsylvania Bird Atlas (PBA3) project, will set an important baseline for data on the distribution and abundance of the state’s winter avifauna.