Assistant-report selection gave no clear temperature-slope change in Canada and US bird surveys in 1985-2024

We tested whether requiring assistant status changes the start-temperature slope of recorded bird taxa. We used 72,953 consecutive-year pairs with the same route and observer in Canada and the US, in 1985-2004 and 2005-2024. The requirement removed 2.5-34.5 percent of pairs. Complete-record minus all-record slopes ranged from -0.054 to +0.027 taxa per 5 C. All four adjusted intervals included zero. All primary intervals were inside -0.25 to +0.25 taxa per 5 C under the model. Assistant controls, separate year pairs and close survey dates gave no clear change. This is a test of one selection rule, not a test of missingness at random or a causal climate effect. Other missing fields, selected fair-weather runs, detection, model error and shared regional shocks limit use. The package gives source hashes, selected data, code, joint uncertainty and offline checks.

biodiversity · observation bias · missing data · Breeding Bird Survey · temperature · complete cases · null result