Warmer starts near 15 C were linked to shorter US bird survey times in 2005-2024

We tested whether survey-start temperature was linked to elapsed survey time in 64,710 accepted bird survey runs from Canada and the US in 1985-2024. Four country-period models controlled for route-observer effects, state-year effects, start time, date, wind, sky, and assistant status. At a 15 C start, a 5 C warmer temperature was linked to 0.97 minutes less survey time in US records from 2005-2024. The four-test interval was -1.57 to -0.37 minutes. Fair-weather, duration-limit, and route-trend checks kept this estimate negative. The other three main intervals included zero. Adding duration terms changed local temperature-richness slopes by 0.01-0.04 recorded taxa per 5 C. Elapsed time includes travel and recording. Selection, local conditions, shared routes, and changing detection limit inference. We do not estimate causal heat effects, climate change damage, or pollution. The package includes code, the derived panel, exact raw provenance, all results, checks, and a figure.

birds · survey duration · temperature · observation bias · biodiversity · Breeding Bird Survey