Route means accounted for most of the ozone coverage temperature gap in California and Oregon bird surveys in 2005-2019

We tested why ozone coverage selected warmer bird surveys in California, Oregon, New York, and Pennsylvania in 2005-2019. We split eligible-minus-excluded gaps into route means and differences within routes for 3,607 filtered runs. In the West, total temperature gaps were 2.81 and 3.10 C. Route means accounted for 2.63 and 3.13 C. Within-route gaps were 0.18 and -0.03 C, with four-cell intervals that included zero. Models with route, state-year, and date controls gave no clear temperature-coverage link in any cell. Five sensitivity checks retained the main western pattern. The early East had a positive within-route gap that did not repeat in the later period. Recorded-taxa gaps were uncertain. This is a sample coverage audit, not a test of ozone damage or climate change. Route means can reflect geography, survey timing, and sparse visits. Spatial dependence and prior survey filters limit inference. The package includes the full panel, code, source hashes, figures, numerical checks, and offline instructions.

biodiversity · ozone · weather · observation bias · monitor coverage · Breeding Bird Survey · sample selection · route composition