Effective Point-Count Duration for Estimating Bird Species' Richness in Chilean Forests

Pablo M. Vergara, Jaime E. Jimenez, and Roberto P. Schlatter (2010) Effective point-count duration for estimating bird species' richness in Chilean forests. Zoological Studies 49(3): 381-391. When point counts are used to assess species richness or diversity, optimizing the allocation of sampling effort requires that the effective point-count duration be determined that optimizes the species detection rate at each point. In this study, we used species accumulation functions to estimate the effective point-count duration in 6 different Chilean forests. An effective point-count duration was dependent upon forest habitat, the type of accumulation function, and travel time. The effective count durations predicted by 2 different species accumulation functions, the linear dependence and Clench models, increased with increasing travel time. For short travel times (<= 10 min), effective count durations were <= 5 min and slightly shorter than count durations required to reach 80% of the function asymptote. For long travel times (20-30 min), effective count durations were about 7 min, but shorter than count durations required to reach 90% of the function asymptote. These results show that for travel times of 5 min, the use of effective count durations can result in 50% more points. Effective count durations are suggested when a survey is focused on assessing species richness and the presence of common or conspicuous species. http://zoolstud.sinica.edu.tw/Journals/49.3/381.pdf