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Comparison of Point Count Sampling Regimes for Monitoring Forest BirdsAuthor(s): William H. Buskirk; Jennifer L. McDonald
Source: 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. 25-34
Publication Series: General Technical Report (GTR)
Station: Pacific Southwest Research Station
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DescriptionA set of 255 counts was compiled for 13 points using 10-minute periods subtallied at 3 and 6 minutes. The data from each point were subsampled using combinations of count periods, numbers, and schedules to compare the effectiveness of these different regimes at per point coverage. Interspecifically, detection frequencies differed in level and pattern as a function of count period length. The complex nature of detection frequencies is discussed in relation to density and to species-specific activity patterns. Short count periods (3 minutes) are more sensitive to changes in activity levels than long ones. The use of longer periods effectively increases the number of comparable hours for sampling per field day, probably increases the usable length of the field season, and may reduce the effects of observer differences. Analyses of detection frequency data and of species and individual accumulation curves suggest that a point of diminishing returns has been reached well before conducting five 10-minute counts per point. We detect no difference in the effectiveness of same-day and different-day count regimes during our June study period. An increase in count period decreases the number of points that can be surveyed per unit of field time, but increases the total amount of time surveyed. Once between-point time reaches 10 minutes, the count period has little effect on the number of points at which many species are detected per unit of field time. Because data from each has different applications, we recommend that a 10-minute count period with 3- and 5- minute subtotals be used for some monitoring regimes. The selection of the number of repeat counts per point depends on the purpose of the project, but for most monitoring applications three or fewer surveys should be conducted per point per season.
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CitationBuskirk, William H. ; McDonald, Jennifer L. 1995. Comparison of Point Count Sampling Regimes for Monitoring Forest Birds. 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. 25-34
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