First-year status gave no repeated ozone slope difference in four US bird samples in 1995-2024

We tested whether the link between prior-season ozone and recorded bird species richness differed in an observer's first recorded US survey year. We used a verified panel from the US Breeding Bird Survey, EPA ozone, and NOAA county weather. Four separate East and West samples in 1995-2009 and 2010-2024 used route-observer and state-year effects, survey controls and weather terms. The slope differences were -0.67, +1.01, +0.81, -0.43 recorded species per 10 ppb ozone. Only the later eastern difference excluded zero after correction for four tests. Its corrected interval was +0.06 to +1.96 species. Its interval included zero with route trends. No repeated difference was found. The first-year flag measures entry to the US archive, not entry to a route. The test cannot separate detection, site selection and ecological change. Few western state clusters, coarse exposure and selected observer spells limit inference. The package includes the exact input, source hashes, code, all results and a numerical check.

ozone · biodiversity · bird surveys · observer experience · observation bias · regional replication · weather controls