A Retrospective Perspective: Evaluating Population Changes by Repeating Historic Bird Surveys

Lawrence D. Igl and Douglas H. Johnson

Abstract: Acquiring an accurate picture of the changes in bird populations often involves a tradeoff between the time and effort required to complete the surveys and the number of years spent surveying the bird populations. An alternative approach to long-term monitoring efforts is to collect current data and contrast those with data collected earlier in a similar fashion on the same study site(s). To evaluate changes in bird populations, we repeated two extensive surveys, one in North Dakota (1967 vs. 1992-1993) and the other in the Platte River Valley of Nebraska (1979-1980 vs. 2001), where large areas of native vegetation had been converted to agriculture. We use these examples and others from the literature to illustrate the advantages and disadvantages of using historical data as a frame of reference for population changes.

Key words: bird populations, historic surveys, long-term monitoring, Nebraska, North Dakota, population changes.

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This resource is based on the following resource (Northern Prairie Publication 1473):

Igl, Lawrence D., and Douglas H. Johnson. 2005. A retrospective perspective: evaluating population changes by repeating historic bird surveys. Pages 817-830 in C. J. Ralph and T. D. Rich, eds. Bird conservation implementation and integration in the Americas: proceedings of the third international Partners in Flight conference, March 20-24, 2002; Asilomar, California. U.S. Dept. of Agriculture, Forest Service, Pacific Southwest Research Station, Albany, CA. U.S. Forest Service General Technical Report PSW; PSW-GTR-191.

This resource should be cited as:

Lawrence D. Igl and Douglas H. Johnson, Northern Prairie Wildlife Research Center, U.S. Geological Survey, 8711 37th Street SE, Jamestown, ND 58401. E-mail: larry_igl@usgs.gov.