An observer's first year on a route gave no clear change in survey temperature slopes in four US bird samples in 1995-2024

We tested whether survey-start temperature had a different link to recorded bird richness in the first year an observer surveyed a route. We used a signed public-data panel and full US survey history to define first years. Four tests covered eastern and western US routes in 1995-2009 and 2010-2024. Adjusted slope differences ranged from -0.16 to +0.07 recorded species per 5 C. All corrected intervals included zero. This does not establish equal slopes. Full history also showed that 1,636 of 5,126 apparent first visits in the selected panel were later visits. Selected routes, few western state clusters and uncertain detection limit inference. This is not a causal climate or pollution effect. Code, inputs, source hashes, results and numerical checks are included.

birds · observation bias · temperature · first-year observer · species richness · regional replication