Publication Details

Analysis of Sample Size, Counting Time, and Plot Size from an Avian Point Count Survey on Hoosier National Forest, Indiana

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Thompson, Frank R.; Schwalbach, Monica J.

Year Published

1995

Publication

In: Ralph, C. John; Sauer, John R.; Droege, Sam, technical editors. 1995. Monitoring bird populations by point counts. Gen. Tech. Rep. PSW-GTR-149. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 45-48

Abstract

We report results of a point count survey of breeding birds on Hoosier National Forest in Indiana. We determined sample size requirements to detect differences in means and the effects of count duration and plot size on individual detection rates. Sample size requirements ranged from 100 to >1000 points with Type I and II error rates of <0.1 and 0.2. Sample size was inversely related to species abundance (r = -0.38, P < 0.01). Counting efficiency was maximized at a count duration <6 minutes with a travel time of 8 minutes, but differences were slight for most travel times. Unlimited-radius plots detected more individuals than 50-m or 70-m radius plots (P < 0.05). We recommend serious consideration of Type II error when designing monitoring protocols. Secondary study objectives and the need for standardization should be weighed heavily when selecting counting time in the range of 5 to 10 minutes. We recommend the use of unlimited-radius plots while simultaneously recording individuals relative to a fixed radius.

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Citation

Thompson, Frank R.; Schwalbach, Monica J. 1995. Analysis of Sample Size, Counting Time, and Plot Size from an Avian Point Count Survey on Hoosier National Forest, Indiana. In: Ralph, C. John; Sauer, John R.; Droege, Sam, technical editors. 1995. Monitoring bird populations by point counts. Gen. Tech. Rep. PSW-GTR-149. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 45-48

Last updated on: January 13, 2009