Partner in Flight Landbird Population Estimates Database, Version 2004

The population size estimates in this database correspond to those presented in the Partners in Flight North American Landbird Conservation Plan (Rich et al. 2004) and The Association of Fish and Wildlife Agencies Partners in Flight Landbird Reports (Rosenberg 2004) . These estimates were derived from Breeding Bird Survey data from the 1990’s, and thus reflect average population sizes during that decade.

Why estimate landbird populations?

In developing the North American Landbird Conservation Plan, PIF made the first attempt to estimate the population sizes for roughly 448 North American landbird species. 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.2005 ), 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.


How to use and interpret the population estimates database

Partners in Flight acknowledges that 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 are described fully in the accompanying Guide to the PIF Population Estimates Database, and we urge all users of the database to use the Guide 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.