Observer experience curves gave no clear change in ozone by warmth slopes for US bird richness in four samples in 1995-2024

We tested whether curved changes with observer experience alter an ozone by warmth slope for recorded bird richness. We used a verified public panel from the US Breeding Bird Survey in four East and West, early and late samples. The fits used 31,108 accepted surveys. Route-observer and state-year effects absorb linear years since observer debut exactly. Added quadratic and cubic experience terms changed the interaction coefficient by -0.0066 to +0.0055 species per 10 ppb ozone and 1 C. All four paired change intervals included zero after correction for four tests. All adjusted interaction intervals also included zero. Hinges at 5, 15 and 30 years gave the same broad result. This checks a common experience curve. It does not rule out observer aging, individual drift or a pollution effect. Experience is not age. Selected routes, coarse weather, exposure error and few western state clusters limit inference. Code, aggregate results, source hashes and retrieval steps are included.

observer experience · bird richness · ozone · warmth · observation bias · fixed effects · null result