Ozone gave no clear increase in annual bird-count variation with seasonal temperature changes in US surveys in 1995-2024

We tested whether ozone increased the link between absolute seasonal temperature changes and absolute annual bird-count changes. We used a published panel of US Breeding Bird Survey records, EPA ozone, and NOAA weather. The pooled model used 17,651 consecutive-year pairs on 1,801 routes with the same observer. It included route-observer and state-year effects and survey controls. The interaction was -0.78 in 100 times absolute log-count change per 2 C temperature change and 10 ppb mean ozone. Its 95% interval was -2.06 to +0.51. All four East and West, early and late estimates were negative. All corrected intervals included zero. Closer monitors, count-change capping, and route trends gave the same broad result. A pooled signed-change signal did not repeat across the four samples. These tests measure recorded count changes, not population stability. Coarse weather and exposure, changing detection, selected routes, and few western state clusters limit inference. The package contains the source panel, exact pairs, code, source hashes, estimates, and a numerical check.

ozone · bird counts · annual variation · temperature change · observation bias · regional replication · null result