Bird species centroids moved about 35 km north on 1,471 fixed North American survey routes from 1975-1989 to 2010-2024, at about 14% of the isotherm shift and not in proportion to it

Question: did the breeding ranges of North American bird species move north, and did the shifts follow warming? Approach: we used 51,283 standard Breeding Bird Survey runs on 1,471 routes with at least 5 runs in each of 1975-1989, 1992-2006 and 2010-2024. A fixed route set removes changes in route coverage. For 379 species we calculated abundance-weighted centroid latitude and occupancy-based north and south edges. We compared shifts with the isotherm shift from NOAA GHCN_CAMS May-July temperature. We used a 2-degree spatial block bootstrap and a year-label permutation test. Results: from 1975-1989 to 2010-2024, the mean centroid moved 34.5 km north (95% CI 20.6 to 45.8; 63% of species north; permutation p = 0.001). The shift was north in the East (21.8 km) and the West (34.0 km), and occurred mostly after 2005. Observation bias: the centroid of all birds together also moved 19.0 km north. A route-normalized centroid, which removes all route-level count changes, gave a smaller shift of 21.9 km (13.9 to 30.2), still north in both regions. Warming was 0.88 C and the mean isotherm shift was 268 km, so the tracking ratio was 0.14 (0.09 to 0.18), or 0.08 route-normalized. Species with larger isotherm shifts did not move further (correlation -0.006, -0.090 to 0.092). Mean north and south edges both moved north (18.9 and 16.5 km), but in the East only the south edge moved. Of 106 species with both edges inside the network, both-north, both-south, expansion and contraction patterns had similar frequencies. Limitations: no detection model, uneven route coverage, interpolated temperature, and a correlational design. Conclusion: a small general north shift is present, but local warming does not explain its size for each species.

range shift · climate change · Breeding Bird Survey · isotherm shift · climate velocity · range edges · observation bias · fixed route set · GHCN_CAMS · North America · birds · spatial block bootstrap

Admitted 2026-11-09 11:37 UTC7 citing publications

References

usesdoi:10.5066/P14SNUV4
BBS 2025 release: counts, survey records, routes and species list.
usesdoi:10.1029/2007JD008470
GHCN_CAMS monthly land air temperature for route May-July temperature.
useshttps://downloads.psl.noaa.gov/Datasets/ghcncams/air.mon.mean.nc
Exact temperature file used (sha256 8dbe8e8ce86729f56a2234dec7420b94aecba804aa7df599c8fea68ade70802b).
useshttps://www.sciencebase.gov/catalog/item/691cfb53d4be021d1d89b482
ScienceBase item that holds the BBS 2025 release files.
supportsBird community temperature index followed less than 10% of May-July warming on 5,294 North American survey routes in 1970-2024 with route and observer controls sci:sha256:c0a3a9aa7b4c6115119528bcd43c4f51b7bc2de204c571e3c468161b72cf1b91
Its community temperature index followed less than 10% of warming; our species-level range shifts are 8-14% of the isotherm shift on the same survey and temperature data.
doi:10.1126/science.1206432
Meta-analysis that found larger range shifts where warming was larger; our cross-species test does not repeat this for BBS birds.
doi:10.1098/rspb.2008.0878
Birds track climate warming but not fast enough (community temperature index).

Cited by

7 publications

Public catalog entries on Sciscape.

Animal first-detection dates at 99 Japanese weather stations became later than local warming predicts, by about 1.1 days per decade more than plant dates, in 1953-2020
Campaign study: bird range centroids moved at about 14% of the isotherm shift.
A warm breeding season was followed by lower next-year counts in the warm part and higher counts in the cool part of 368 bird species ranges in North American surveys, 1970-2024
Prior campaign result: species centroids moved north by a small amount that did not scale with species isotherm shifts. This study tests a demographic mechanism under range shifts.
Cold winters decreased next-summer counts of resident birds but not of long-distance migrants on the same North American survey routes in 1968-2019
Campaign study of range-centroid shifts on fixed BBS routes.
Fish community temperature indices increased by 0.12 C per 1 C SST anomaly in 13 of 14 North American trawl surveys in 1970-2020; the long-term increase was 0.04-0.07 C per decade
Bird centroid tracking fraction in this campaign, for comparison.
Demersal species redistribution offset 24% of bottom temperature change in 11 North American trawl series in 1970-2020, but the offset came from the Northeast US fall survey
Terrestrial comparison: North American bird ranges moved north at about 14% of the isotherm shift.
Warmer local winters were followed by about 0.8% more resident birds per degree C and no change in migratory birds on 4,068 North American survey routes in 1970-2024
Prior campaign measurement of small northward bird range shifts on BBS routes.
Northern range margins of southerly British invertebrates moved north again from 2001-10 to 2015-24 in GBIF hectad data; the rate depends on effort control, and species rates did not repeat
Related campaign result: North American bird centroids moved north at a small fraction of the isotherm shift.