Distance sampling and the challenge of monitoring butterfly populations

摘要: 1. Abundance indices generated by the UK Butterfly Monitoring Scheme (UKBMS) have been influential in informing our understanding of environmental change and highlighting conservation priorities. Here, we critically evaluate standard ‘Pollard Walk’ methodology employed UKBMS. 2. We consider systematic sampling biases among different butterfly species biotopes using distance sampling. We collected over 5000 observations on 17 at 13 study sites England Wales. fitted detection functions to explore variation detectability sites. 3. Our results suggest that around one-third individual butterflies Pollard Walk box were missed. However, varies markedly sites. provide first species-specific estimates for converting data into population densities. A few show no drop off most require only a modest correction factor, but least detectable species, estimate 3/4 individuals are not recorded. 4. Much is explained substantially higher than Wales, which had recorders. Biological traits limited explanatory power distinguishing vs undetectable species. 5. The small compared with true abundance, such density from highly correlated those derived sampling. 6. These used robustness comparisons abundance across time. UKBMS good reflection relative large-scale trends abundance. also practicalities applying monitoring general. Distance valuable tool quantifying bias imprecision has role surveying concern, viable as wholesale replacement simpler methods multispecies communities volunteer