NEON point-count trends agree weakly with nearby Breeding Bird Survey trends at 42 US sites in 2017–2024; after correction for sampling noise and year shocks, the trend correlation is about 0.5

Question: Does a bird population trend at one NEON site estimate the trend in the region around it? Data: NEON breeding landbird point counts (RELEASE-2026, via neonDivData) and North American Breeding Bird Survey (BBS) routes within 100 km of each site, 2017–2024. The main set has 1,196 site × species pairs: 42 sites, 254 species, 20,885 NEON point-years and 2,264 BBS runs. Method: Poisson log-linear trends with point or route-observer fixed effects. We used 100 random split halves of points and routes to get the reliability of each program, and detrended annual indices of the halves to estimate year shocks in each program. Intervals come from a bootstrap of 21 site clusters. Simulations on the real designs validated the estimators. Results: The observed Spearman correlation of NEON and BBS trends was 0.19 (95% CI 0.15–0.24). Split-half reliability was 0.78 for NEON and 0.42 for BBS. Two BBS halves agreed better with each other (0.27) than with NEON halves (0.15). Correction for sampling noise gave 0.34 (0.25–0.42). A further correction for year shocks gave a persistent-trend correlation of 0.49 (0.31–0.79). Year shocks were 29% of the reliable NEON variance. One NEON site predicted the trend of the other nearby BBS routes as well as the nearest single BBS route (0.20 vs 0.21). Detrended annual fluctuations agreed at r = 0.06. Sensitivity sets (50 or 200 km radius, detections ≤100 m) gave persistent correlations of 0.38–0.53. For pairs with at least 100 birds in each program, the value was 0.82 (0.57–1.20), and full agreement was not excluded. Limitations: eight years only, no detectability model, no NEON observer identity, log-linear trends. The remaining disagreement can be real local-versus-regional difference or persistent method differences. These data cannot separate them.

NEON · Breeding Bird Survey · population trends · monitoring · point counts · split-half reliability · measurement error · disattenuation · year effects · birds · spatial scale · survey comparison