Breeding bird synchrony on North American BBS routes did not increase from 1970–1994 to 2000–2024 when years are resampled, at route and 2° cell scales
Question: Koenig and Liebhold (2016) reported increasing spatial synchrony of wintering birds and of temperature in 1960–2009. Two SCI studies found no increase in Breeding Bird Survey (BBS) data, but did not quantify the effect of shared years on their confidence intervals. Approach: We used BBS 1966–2024 (5,306 routes). We calculated the Pearson correlation of within-observer growth rates in 1970–1994 and 2000–2024 for fixed route pairs (96 species, ≤100 km) and for fixed panels of routes averaged in 2° cells (122 species at ≤400 km, 129 at ≤1000 km). We resampled years in blocks of 3, adjusted for changes in mean count, simulated power with the real pair structure, and applied the 5-year-window metric of the original study. We also tested the temperature trend in 5-year windows with CRU TS 4.10 Tmax and mean temperature. Results: The change in mean synchrony was −0.0038 for routes (95% CI −0.0155 to +0.0075 with years resampled), −0.0044 for cells at ≤400 km (−0.027 to +0.015) and −0.0076 at ≤1000 km (−0.023 to +0.007). Year-resampled intervals were 1.3 to 1.5 times wider than species-resampled intervals. A simulated true increase from 0.20 to 0.25 gave an observed change of +0.013, which the upper bounds exclude. With the original 5-year metric, 34 of 78 species (44%) had positive trends; the CBC study reported 63–69%. Summer Tmax synchrony increased in windows that start 1961–2005, but not over 1961–2020. The annual mean-temperature increase at ≤1000 km disappeared when we removed the windows that start in 1961–1967. Limitations: The input data are the same as in the earlier SCI studies. Count noise attenuates observed correlations, so smaller latent changes are not excluded. Each bootstrap keeps one source of variation fixed. We did not reanalyse CBC or station data.
spatial synchrony · Breeding Bird Survey · Moran effect · replication · block bootstrap · population dynamics · temperature synchrony · CRU TS · statistical power · North America
References
7- challengesdoi:10.1038/nclimate2933
We test whether the reported increase in bird and temperature synchrony occurs in BBS breeding birds and in gridded temperature with the same windowing; the bird increase does not occur and the annual temperature trend depends on the first windows.
- supportsSpatial synchrony of 183 breeding bird species did not increase on North American BBS routes in 1967–2024, while summer temperature synchrony at the same routes increased sci:sha256:0ce6bd66e8d562c2352cc37877f84b30f18b32f5c80febffe1d8aabc2c47fc83
Independent code and design on the same BBS release gives the same null bird result; we add year-block bootstrap intervals, cell panels and a power simulation.
- supportsSpatial synchrony of 168 North American breeding bird species did not increase in 1970–2024 BBS data at 0–1000 km, although winter temperature synchrony on the same route pairs increased sci:sha256:c05019daf107b96a1569a4c34dfaf4108c75733d8639064bfb04fb1b2313c18b
Same null bird result with fixed route pairs and 2-degree cells; our year resampling quantifies the shared-year limitation that this study states.
- usesdoi:10.5066/P14SNUV4
BBS 1966-2024 counts, routes and observers.
- usesdoi:10.1038/s41597-020-0453-3
CRU TS 4.09 and 4.10 tmp and tmx.
- usesdoi:10.1029/2007JD008470
GHCN-CAMS monthly temperature.
- doi:10.1111/cobi.13662
Earlier BBS test of change in synchrony of grassland birds.
Cited by
0 publicationsPublic catalog entries on Sciscape.
No incoming citations on Sciscape.