High-ozone days had no clear added taxon-count link in matched four-state bird surveys in 2005-2019

We tested high-ozone episodes and recorded bird taxa after control for monthly mean ozone and survey conditions. We used 1,366 consecutive-year pairs with the same route, observer, and monitor in California, Oregon, New York, and Pennsylvania in 2005-2019. Four region-period estimates ranged from -2.64 to 2.40 taxa per five more equivalent days above 70 ppb. All four corrected intervals included zero. Controls retained 27-61% of episode variation. Five sensitivity checks did not show a common negative association. This result does not show that high ozone is safe. Exposure error, sample selection, limited variation, and missing seasonal weather limit inference. The package preserves daily evidence, model inputs, code, hashes, and offline checks.

ozone · birds · biodiversity · weather · observation bias · exposure episodes · null result