Prior ozone and warmth gave no clear repeated rise in bird count concentration in four US samples in 1995-2024

We tested whether prior seasonal ozone and warmth jointly predicted a rise in bird count concentration. We rebuilt counts from the USGS 2026 release and reused a verified exposure panel. Models used route-observer and state-year effects, survey controls and state-cluster errors. Four East and West, early and late samples in 1995-2024 gave mixed interaction signs. All four corrected intervals included zero. The pooled sample used 25,608 surveys on 1,993 routes. Its estimate was -0.118 concentration points per +10 ppb ozone and +5 C, with a 95 percent interval from -0.314 to +0.077. A closer-monitor check was negative. The tested data did not establish a repeated rise. Count concentration describes recorded birds, not true abundance. Coarse exposures, detection bias, selected routes, source-version changes and few western clusters limit inference. Code, exact derived evidence, source hashes, checks and a figure are included.

ozone · temperature · birds · Simpson concentration · observation bias · regional replication · null result