Characteristics of data from bird sound recordings-relations between unit recording length and increasing rates of cumulative number of species.

概要

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The occurrence rates of bird species estimated by hearing sound recordings (frequency of recordings where the species appeared/total number of recordings) differed significantly among species. The species that were listed when the number of recordings increased had smaller occurrence rates. The ratios of the number of species with higher occurrence rates to the total number of species listed, therefore, became smaller with increasing numbers of recordings. Thus, the cumulative number of species increased logarithmically with the elapsed time (i.e. the number of recordings). The shorter the unit recording length, the greater the increasing rates of the cumulative number of species, when the cumulative number of species is plotted to elapsed time using bootstrap resampled data. The resampling procedure provides the repeated trials, and the detection probability of the species is described as 1-(1-p)n, where p is the occurrence rate of the species and n equals the number of trials. In species for which the frequency of recordings increases as the unit recording length shortens, the shorter the unit recording length, the greater the detection probability for a certain time period, and as a result to be listed for a shorter time on average.
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