June-August mean control kept positive spring flight-spread slopes in two English Meadow Brown samples in 2000-2024

We tested whether summer mean temperature removes a positive spring link to Meadow Brown flight-date spread. Four English region and period models used 18,424 site-years in 1976-2024. With site intercepts, time and June-August temperature control, March-May slopes were +0.60 and +0.88 days of flight-date standard deviation per C in the North and South in 2000-2024. Both four-test intervals were above zero. Early northern evidence was unclear. Separate June, July and August controls reduced the later northern slope to +0.22, with a marginal interval that included zero. The tested summer mean alone did not remove the later spring link, but the result depends on the weather model. Shared source records, selected sites, coarse weather and missing visit-level effort limit inference. The package gives verified source lineage, direct raw checks, derived data, code, uncertainty and a static figure. No causal climate or pollution effect was tested.

phenology · butterflies · seasonal temperature · observation bias · Meadow Brown · flight spread · model sensitivity