Comparison of trends in butterfly populations between monitoring schemes

Abstract

for research. Most schemes sample sites that are self-selected by contributors and therefore tend 20 to cover locations that are rich in butterflies. To provide a more representative assessment of 21 butterfly populations, the Wider Countryside Butterfly Survey (WCBS) was developed with a 22 stratified-random sample of survey sites across the UK. We compare butterfly trends from the 23 WCBS locations against those measured from traditional butterfly transects which are typically 24 located in areas of good quality semi-natural habitats. Across the 26 species analysed, there was a 25 significant positive relationship between trends measured from the two schemes between 2009 and 26 2013, the period when both schemes were operating fully. There was a tendency (17 out of 26 27 species analysed) for these changes to be greater within WCBS compared to traditional BMS 28 transects, although this effect was not consistent across comparisons between pairs of consecutive 29 years. When assessing these individual year-to-year changes, there was however a significant 30 correlation between the two schemes in all cases. Over relatively short time periods, weather 31 patterns are likely to dominate butterfly population fluctuations and lead to comparable trends 32 across monitoring schemes. Over longer time periods, differences in land management may affect 33 habitat condition differently for protected areas versus the wider countryside and it is therefore 34 important to maintain comprehensive butterfly monitoring programmes to detect and interpret 35 such effects. 36 3

Using citizen science butterfly counts to predict species population trends

“…This compares favorably with the value of 0.75 obtained by Roy et al. () when they compared population trends from the UKBMS with the Wider Countryside Butterfly Survey, in which a reduced‐effort UKBMS sampling protocol is used in randomly selected locations (Brereton et al. ).…”

“…Following Roy et al. (), we determined annual population growth rates for each species from the 2 data sets. In brief, we defined as the expected total count of a species at site i in year t across visits, and regarded this as the realisation of a Poisson random variable.…”

Simplified and still meaningful: assessing butterfly habitat quality in grasslands with data collected by pupils

“…Although we aggregated data from four expert surveys in two consecutive years for the calculation of BHQ to reduce the effect of short term population fluctuations, the relatively short time period of our survey weakens its informative value regarding absolute habitat quality. However, population fluctuations of butterfly species are generally similar over large areas and therefore relative values of population index comparing different sites remain fairly stable (Pollard and Yates 1993;Roy et al 2015). Thus we are confident that BHQ is a suitable metric to compare different sites and to estimate the explanatory power of the simplified butterfly assessment conducted by laypeople.…”

Ecological monitoring with citizen science: the design and implementation of schemes for recording plants in Britain and Ireland

“…those targeted by the traditional transect location of the UKBMS). Initial results from the WCBS suggest that the trends are similar with either approach (Roy et al ., ). Given existing knowledge of the importance of high‐quality habitat for many specialist butterflies (Warren et al ., ), and the fact that they are generally highly mobile organisms (Thomas, ), this result is not unexpected; however, without the WCBS, it would be impossible to know with any degree of confidence whether nature reserves were different from the wider countryside for commoner butterfly species, or to detect increases in the ranges or abundances of our rarer species occurring outside of the potentially biased set of traditional UKBMS sites.…”