Spring warmth gave no clear repeated link to the butterfly survey-coverage gap in England and Wales in 1980-2024

We tested whether spring warmth was linked to a larger difference in insufficient survey coverage between Orange-tip and Meadow Brown butterflies. We paired both species at the same site and year in England and Wales. Four separate country and period models used 26,245 paired records in 1980-2001 and 2002-2024. Models controlled fixed site differences, rain, summer temperature and linear time. Spring warmth slopes ranged from -5.17 to -0.18 percentage points per C. All four intervals with a four-test correction included zero. The proposed positive link did not repeat. Early Wales had only 19 sites and a wide interval. This is a test of index availability among paired source rows. It does not test all absent records, causal climate effects or pollution. The package gives source hashes, paired data, code, figures and independent checks.

butterfly · observation bias · survey coverage · phenology · spring temperature · UKBMS · null result