Warm seasons gave no clear ozone interaction in US bird count ratios in 1995-2024

We tested whether a warm previous breeding season changed the link between ozone and the ratio of passerine to other bird counts. We used a verified public-data panel of US Breeding Bird Survey records, EPA ozone, and NOAA county weather. The pooled model used 31,388 accepted surveys on 2,024 routes in 1995-2024. It included route-observer and state-year effects and weather and survey controls. The interaction was -0.0139 log ratio units per +10 ppb ozone and +5 C temperature anomaly, with a 95% interval of -0.0390 to +0.0111. Four separate East and West, early and late samples gave mixed signs. All four intervals included zero after correction for four tests. Route trends, closer monitors, and other ratio forms gave the same broad result. This taxonomic contrast does not measure diet, abundance, or climate-change effects. Coarse exposures, monitor selection, unknown detection changes, small western cluster counts, and temperature scaling limit inference. The package includes the exact input panel, raw source recipes and hashes, code, all estimates, a numerical model check, and a figure.

ozone · seasonal temperature · bird counts · community composition · observation bias · regional replication · null result