March warmth gave no clear repeated link to first-week Orange-tip sightings in England and Wales in 1980-2024

We tested whether warm March conditions put more first Orange-tip sightings in the first survey week, 1-7 April. We used 19,758 site-years in four country and period samples. The three samples with first-week events had positive estimates of 2.22, 4.02 and 2.26 percentage points per C. All three intervals with a four-test correction included zero. Early Wales had no first-week events and cannot support this slope test. The data do not establish the proposed repeated link. They do not show that survey start dates cause no bias.

phenology · Orange-tip · observation bias · survey season · temperature · regional replication · null result