Population Estimates Database: About the Database

The Population Estimates Database and Handbook are products of the PIF International Science Committee and are supported with funding from the Bureau of Land Management, Department of Defense-Partners in Flight, the US Fish and Wildlife Service, and U.S. Forest Service, as well as through significant in-kind contributions from Canadian Wildlife Service, Cornell Lab of Ornithology, and other partners. Additional financial support for the Population Estimates and Species Assessment Databases will ensure their long-term maintenance and usefulness. To contribute, click here and select 'PIF Database' in the dropdown box.

What’s new in Version 2

This version of the PIF Population Estimates Database corresponds with the Partners in Flight Species Assessment Database (version 2012) and Saving our Shared Birds: the Partners in Flight Trinational Vision (Berlanga et al. 2010). It is intended to replace the previous version, which corresponded with continental population estimates used in the PIF North American Landbird Conservation Plan (Rich et al. 2004) and stepped-down population estimates for each U.S. state in The Association of Fish and Wildlife Agencies Partners in Flight Landbird Reports (Rosenberg 2004).

Version 2.0 incorporates more recent data from the North American Breeding Bird Survey, additional population data sources, new independent estimates, and other modifications. Details related to changes in this update are provided in the Handbook to the Partners in Flight Population Estimates Database, version 2.0. Details on the original Population Estimates Database and the underlying estimation methodology are provided in the Guide to the PIF Populations Estimates Database (version: North American Landbird Conservation Plan 2004). Partners in Flight continues to seek input and relevant data from throughout the bird-conservation community to improve these estimates. To provide feedback on PIF population estimates, please contact the PIF Database Manager.

Why estimate landbird populations?

Estimates of population size are an important component of bird-conservation planning for several reasons. First, an order of magnitude category of global population size is one of six factors used to assess overall conservation vulnerability as part of the PIF species assessment process (see Panjabi et al. 2012), with species having smaller global populations being more vulnerable than species with larger populations. Second, even crude estimates of population size serve to underscore the magnitude of our task to restore and conserve populations of declining common birds, often involving millions of individual birds that will require millions of acres of restored or improved habitats. As such, these estimates may serve as the first step in setting quantitative conservation objectives within states or Bird Conservation Regions, and an important component of Conservation Design. Finally, order-of-magnitude population estimates provide a basis for comparing independent estimates of concentrations of birds during migration and especially avian mortality from anthropogenic sources such as communication towers, buildings, or cats.

In developing the North American Landbird Conservation Plan (Rich et al. 2004) , PIF made the first attempt to estimate population sizes for roughly 448 North American landbird species, primarily using data from the North American Breeding Bird Survey from the 1990’s. Version 2.0 update replaces those estimates incorporating more recent BBS data from 1998-2007, in addition to other new data sources such as the Ontario Breeding Bird Atlas, numerous species-specific surveys, reviewer feedback and other changes.

How to use and interpret the population estimates database

The science behind estimating bird populations is imprecise and evolving. A vast majority of the estimates are derived from relative abundance data from the North American Breeding Bird Survey, which was not developed for this purpose. The general concepts and methodology used by PIF are described in Rosenberg and Blancher (2005), and Appendix 3 of the PIF North American Landbird Conservation Plan (Rich et al. 2004). A critique of these methods, with useful recommendations for improvement was published in the Auk (Thogmartin et al. 2006).

Because of the many assumptions and uncertainties involved with estimating population size, PIF includes a series of important caveats and color-coded data-quality flags into the population estimates database and downloadable tables and spreadsheets. These caveats and all other details pertaining to the population estimation process are described fully in the original Guide to the PIF Population Estimates Database, and the accompanying Handbook to the PIF Population Estimates Database, version 2.0. We urge all users of the database to use these resources while interpreting the numbers in this database. Nonetheless, the PIF population estimates can be an important tool for conservation planning and implementation at several geographic scales.

Rocky Mountain Bird Observatory 2013