Common ozone sites gave no clear change in warmth interactions for US bird richness in 1995-2024

We tested whether changes in available ozone sites altered an estimated ozone by warmth link to recorded bird richness. We used 23,267 consecutive-year survey pairs on 1,991 US bird routes, with the same observer in each pair. Both exposure methods used sites within 50 km. One method used each year’s available sites. The other used only sites present in both years. Four East and West, early and late models controlled survey conditions and state-year effects. Common minus available interaction slopes ranged from -0.084 to +0.042 taxa per 10 ppb ozone and 5 C warmth. All four paired state-cluster intervals included zero after correction for four tests. Route trends and total bird counts gave the same broad result. This does not show equal exposure accuracy or no ecological harm. Selected roadside routes, coarse seasonal weather, missing daily data, few western state groups and detection bias limit inference. The package includes source hashes, paired data, code, numerical checks and a figure.

ozone · temperature · bird richness · observation bias · monitor availability · paired model comparison · null result