Changes in version 2.0 of the Partners in Flight Population Estimates Database are detailed
in the Handbook to the Partners in Flight Population Estimates Database, version 2.0.
The version 2.0 Handbook is a companion document to the original Guide to the PIF Population Estimates Database,
which describes in full the contents of the database and provides an overview
of the process used to generate the estimates using data from the North American Breeding
Bird Survey, including potential uses of the data, caveats, and future directions for revising these estimates.