Do feeder counts reliably indicate bird population changes? 21 years of winter bird counts in Ontario, Canada
This study compared estimates of changes in bird populations that were calculated from data submitted by Project FeederWatch (PFW) participants with trends calculated by data from Christmas Bird Counts (CBC). Trends calculated by PFW and CBC from 1976 – 1997 in Ontario, Canada were compared. For most species, PFW and CBC data produced similar results. The consistency between surveys suggests that they are both useful for monitoring bird populations. However, the two surveys did not agree on some species. For instance, Blue Jay, Downy Woodpecker and Hairy Woodpecker population trends did not agree between the two survey methods. These results highlight the importance of having two independent surveys in order to corroborate estimates of population trends. The authors conclude that Christmas Bird Counts have the advantage in that they involve more species, but Project FeederWatch has a more consistent protocol that continues throughout the winter. The November – April study period of PFW allows analysis of changes in populations throughout the winter.
This article was written by Denis Lepage and Charles Francis of Bird Studies Canada, which operates Project FeederWatch in Canada. It appeared in the May 2002 issue of The Condor, an international journal that publishes scientific articles on the biology of wild species of birds.