Rainfall deficits gave no clear repeated change in ozone-temperature slopes at US bird survey routes in 1995-2024

We tested whether low May-June rainfall strengthened the link between May-June maximum temperature and April to mid-June ozone at US bird survey routes. Four region and period models used 32,956 accepted surveys in 1995-2024. Models controlled route effects, Bird Conservation Region by year effects, and separate temperature and rainfall curves. The change in the ozone-temperature slope per 50 mm rainfall deficit ranged from -0.008 to +0.088 ppb per C. All four corrected intervals included zero. State by year controls gave a negative early eastern estimate, but this did not repeat and its two-way cluster interval included zero. Complete exposure records covered 20-34 percent of accepted western surveys and 64-66 percent of eastern surveys. The result tests exposure structure in a biodiversity sample. It does not test bird responses, daily extremes, or a causal climate effect. Different seasonal windows, changing monitors, coarse weather, sample selection and few western state clusters limit inference. Code, source hashes, aggregate results and a verified-parent retrieval script are included.

ozone · temperature · rainfall · exposure design · biodiversity · observation bias · null result