Abstract
The relationships between the number of surveys and the estimation accuracy of bird flight frequency based on vantage point observation were examined using the nonparametric bootstrap method. In the case of 50 2-hour surveys, the mean flight frequencies of Slaty-backed Gulls and crows which were consistently detected in the study site were estimated to a precision of ± 25%. In White-tailed Eagles and Black-tailed Gulls which were infrequently observed, on the other hand, their flight frequencies were estimated with a reduced precision. In addition, there was a possibility that a small number of surveys would not show their occurrence in these infrequent species. On the other hand, the changes of relative ratios of 95% confidence interval widths of mean flight frequencies with survey number of times showed approximately similar results for all birds in this study. Therefore, the result of this analysis would contribute to the examination of the number of surveys required for the reliable estimation of bird flight frequency.
