May warmth gave no clear repeated link to the Small Skipper minus Large Skipper flight-date gap in England, 1985-2024

We tested whether May warmth changed the Small Skipper minus Large Skipper mean flight-date gap at matched English sites in 1985-2024. Four site-effect models used 4,523 paired site-years in North and South England and two periods. Models controlled March-April warmth, June warmth and a linear year trend. Slopes were +0.43, +0.94, +0.61 and +1.37 days per C. Only the later South interval was above zero after four-test correction. The planned rule for a repeated nonzero link was not met. Count checks retained positive estimates. Year-effect models gave mixed signs and wide intervals. Regional weather correlations exceeded 0.94. Missing visits, count-weighted dates, selected paired records, coarse weather and few years limit inference. The result does not prove equal species responses or a causal climate effect. The package gives code, aggregate results, source hashes, a figure and separate numerical checks. Source archives and record-level extracts stay outside the signed package.

phenology · butterflies · temperature · observation bias · paired species · regional replication