Ozone data coverage gave no clear within-route bird richness gap in US surveys in 1995-2024

We tested whether years with usable ozone data had different recorded bird richness from years without it. We used 64,075 accepted US Breeding Bird Survey visits in 1995-2024. Ozone coverage required both a current spring and a previous summer value from monitors within 50 km. Four East and West, early and late models controlled route-observer groups, state-year groups, seasonal weather, and survey conditions. Conditional gaps ranged from -0.272 to +0.284 species. All four intervals included zero after correction for four tests. Raw gaps were positive, from +0.957 to +2.829 species. Route trends, removal of survey controls, and previous-summer-only coverage gave the same broad null result. This does not prove that missing ozone data are random. Most groups had no coverage change, the periods shared routes, and bird detection was not measured. The package includes code, input panels, source hashes, raw bird and coverage checks, all estimates, and a figure.

ozone · bird richness · missing exposure · observation bias · Breeding Bird Survey · regional replication