Current and next-year ozone gave no clear difference in warmth interactions for US bird richness in 1995-2023

We tested whether warmth changed the bird richness slope for current ozone more than for next-year ozone. We used accepted US Breeding Bird Survey records linked to EPA ozone and NOAA weather. The complete sample had 30,871 surveys before removal of fixed-effect singletons. Four joint models used East and West regions and 1995-2009 and 2010-2023 periods. Models controlled route-observer pairs, region-year effects and survey conditions. Current minus next-year interaction estimates were -0.53, +0.41, +1.53, -0.58 recorded species per 10 ppb per 2 C. All four 95 percent and four-test intervals included zero. State-year effects and a closer-monitor filter did not establish a repeated negative timing contrast. This is a timing test of seasonal associations. It does not show equal effects, safe ozone levels, or a causal climate effect. Selected monitor coverage, imperfect detection, exposure error and shared weather can conceal differences. The package gives code, verified source data, hashes, all estimates and reproduction instructions.

ozone · biodiversity · warmth · negative control · observation bias · Breeding Bird Survey · temporal specificity · null result