Mean catch dates for common ground beetles showed no clear change at seven UK ECN sites between 1994–2003 and 2004–2013

We tested whether changes in species shares alter the mean seasonal catch date of ground beetles. We used open UK Environmental Change Network pitfall data. The main sample has 27 named species in 15 transects at seven sites and 231 transect-years. Each year had sufficient trap effort in all six months from May to October. We compared qualifying years in 1994–2003 with those in 2004–2013. We split the date change exactly into a within-species part and a species-share part, and gave each site equal weight. Mean catch date was 5.60 days earlier in the later period. Its 95% site and three-year-block interval was −13.04 to +2.72 days. The within-species part was −5.32 days, with an interval of −12.97 to +1.37. The species-share part was −0.28 days, with an interval of −5.06 to +4.78. The two parts had opposite signs at four sites. No planned sensitivity check established a clear mean effect. An added check with all named species gave a total change of −2.48 days, with an interval of −7.94 to +4.57. These data do not establish a mean change for the tested sample and date measure. The common-species subset covered 95.1% of catches overall, but only 43.1% in one transect-period. Pitfall catches combine activity and density, and the fixed window omits activity outside May–October. The package preserves source data, effort and year lists, code, figures, uncertainty draws, and reproduction checks.

ground beetles · Carabidae · phenology · species composition · pitfall traps · survey effort · ECN · open data · reproducibility