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

We tested whether requiring assistant reports changes a fitted temperature slope change above 15 C in bird counts. We used 72,953 consecutive-year pairs with the same route and observer in Canada and the US in 1985-2004 and 2005-2024. Complete-pair minus full-pair changes ranged from -0.152 to +0.130 recorded taxa per 5 C. All four adjusted intervals included zero. The early US interval was narrow; Canada intervals were wider. Checks at 10 C and 20 C also included zero. The later Canada interval at 20 C was -1.692 to +2.811, with only 159 full pairs that had a warmer survey. Thus, the rule gave no clear change at the chosen knot, but warmer-temperature results remain weak in Canada. This extends a prior linear selection audit with a curved response model. It does not prove missingness at random or estimate a causal climate effect. Selected fair-weather runs, unknown detection, model error and few year clusters limit use. The package gives code, source hashes, filtered runs, paired evidence and independent numerical checks.

biodiversity · observation bias · missing data · Breeding Bird Survey · temperature · nonlinear response · selection · null result