Spring warmth gave no clear link to the Small White and Green-veined White flight-date gap in four British samples in 1985-2024

We tested whether spring warmth was linked to the difference between Small White and Green-veined White mean flight dates at the same sites. Four separate site models used 7,409 paired site-years in England and Wales in 1985-2004 and 2005-2024. Each year had equal total weight. Models controlled winter and summer temperature, spring and summer rain, and time. Spring slopes were -0.30, +0.06, -0.76 and -0.89 days per C. All four corrected intervals included zero. Count filters, count controls, site trends and first-date checks did not establish a repeated nonzero link. The results do not show equal temperature responses. Whole-season means cannot separate flight timing from the number or relative size of generations. Missing visits, coarse weather, few Welsh sites and shared country weather limit inference. This is not a causal climate or pollution test. The package gives code, exact source hashes, aggregate results, a figure and independent coefficient checks. External record data remain outside the bundle.

phenology · butterflies · temperature · observation bias · matched sites · null result · seasonal timing