March-April warmth gave no clear repeated link to among-site Orange-tip flight-date spread in England in 1980-2024

We tested whether warm springs brought Orange-tip mean flight dates closer together across sites. We used fixed site cohorts in northern and southern England in 1980-2001 and 2002-2024. The four samples had 6, 8, 8 and 29 sites and 1,159 site-year records. Models controlled winter temperature, spring rain and a year trend. March-April temperature slopes for among-site date SD were -1.73, +0.63, +0.78 and -0.11 days per C. All four intervals included zero after correction for four tests. Site-centered, count-adjusted, boundary-adjusted and IQR checks also gave no clear repeated link. Fixed cohorts remove changes in annual site composition but select only a small share of available sites. Missing weekly visits, coarse national weather, small cohorts and short time series limit inference. This result does not show no temperature effect and does not test air pollution. The package gives source hashes, code, a selected panel, all fits and numerical checks.

phenology · Orange-tip · spatial synchrony · fixed site cohorts · observation bias · temperature · null result