Effects of Point Count Duration, Time-of-Day, and Aural Stimuli on Detectability of Migratory and Resident Bird Species in Quintana Roo, Mexico

Abstract

Effects of count duration, time-of-day, and aural stimuli were studied in a series of unlimited-radius point counts conducted during winter in Quintana Roo, Mexico. The rate at which new species were detected was approximately three times higher during the first 5 minutes of each 15- minute count than in the final 5 minutes. The number of individuals and species detected in 15-minute counts declined by >60 percent over the first 3 hours after sunrise. Use of aural stimuli (playbacks of prerecorded warbler "chip" notes, imitated owl calls, "spishing") offset this temporal reduction in detection rate for Nearctic migrants, but not for most permanent residents. The relative precision of occurrence rates estimated from point count data is inherently low, especially for rarely encountered species. Estimates will be more precise if the sample of points is large and especially if the probability of detecting targeted species is high. Different combinations of sample size and count duration can yield equally precise estimates of occurrence rates.

Parent Publication

• Monitoring bird populations by point counts

Citation

Lynch, James F. 1995. Effects of Point Count Duration, Time-of-Day, and Aural Stimuli on Detectability of Migratory and Resident Bird Species in Quintana Roo, Mexico. 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. 1-6