Next-year minus prior-year index slopes for earlier Meadow Brown flight were below zero in one of four English tests

We tested whether the next-year abundance link to earlier Meadow Brown mean flight dates differed from the prior-year link. We used 6,814 complete three-year records in two English regions and two periods. A direct differenced-outcome model controlled current abundance, spring temperature, site and year effects. Only southern England in 2005-2023 had an interval below zero after correction for four tests: -0.108 log index plus one per ten days earlier flight, with interval -0.185 to -0.031. That result persisted without current abundance, with site trends and with high counts. It became uncertain with first sighting date. The other three tests were uncertain. This exploratory follow-up uses the same records as a prior campaign study. It adds the direct contrast that the prior study did not test. Missing visits, shared count errors, selected complete records and possible effects of prior abundance on timing limit inference. The contrast does not identify a causal climate effect. Pollution and daily extremes were not tested. Code, aggregate results, source hashes, checks and a figure are included.

phenology · Meadow Brown · time order · observation bias · population abundance · direct contrast · temporal replication