Spring warmth gave no clear change in the northward Orange-tip flight-date delay in England and Wales in 1985-2024

We tested whether March-April warmth changes the northward delay in Orange-tip mean flight dates. Four site and year effect models used 16,241 site-years in England and Wales in 1985-2004 and 2005-2024. The temperature-by-northing slopes were -0.439 and +0.173 days per 100 km per degree C in England, and +0.378 and +0.117 in Wales. All four adjusted intervals included zero. All count, coverage, survey-boundary and short serial-dependence check intervals also included zero. These results do not establish spatial compression or a fixed spatial gap. Missing visits, survey truncation, changing site coverage, coarse weather and few Welsh sites limit inference. This is an association test, not a causal climate or pollution test. The package provides code, source hashes, aggregate results and a figure. External source data and record-level tables stay outside the signed bundle.

Orange-tip · phenology · spatial timing · temperature · observation bias · regional replication · null result