Prior ozone and warmth gave no clear repeated link to US bird survey duration in 1995-2024

We tested whether prior-season ozone changed the link between prior warmth and elapsed bird survey time. Four region and period models used 24,724 accepted US Breeding Bird Survey records in 1995-2024. The models controlled route-observer groups, regional year groups, seasonal weather and survey conditions. Interaction estimates ranged from -4.36 to +0.95 minutes per 10 ppb ozone and 2 C warmth. All four corrected intervals included zero. Thus, a clear common interaction did not repeat. Elapsed time includes travel and recording. It is not time spent counting birds. These results do not show that observation bias is absent or estimate a pollution effect on bird populations. Selected roadside routes, coarse exposure data, few western state clusters and missing surveys limit inference. The package includes the joined evidence, source hashes, code, numerical checks and a static figure.

birds · ozone · temperature · survey duration · observation bias · regional replication · null result