Bird 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
Question: did breeding bird communities in Canada and the United States change toward warm-adapted species as fast as the breeding season became warmer? Approach: we used 124,128 standard North American Breeding Bird Survey runs (5,294 routes, 1970-2024) and NOAA GHCN_CAMS gridded temperature. We calculated a cross-fitted Species Temperature Index for 432 species per route half and a Community Temperature Index (CTI) for each run. Fixed-effects models with route and observer effects and two-way clustered errors gave the CTI and temperature trends on the same route-years. Results: the CTI increased by 0.015 C per decade (95% CI 0.007 to 0.023), and May-July temperature increased by 0.249 C per decade (0.177 to 0.322). The tracking ratio was 0.061 (0.029 to 0.093), with almost the same value in the East and the West. All nine sensitivity variants gave less than 10% tracking. The CTI decreased in 1970-1996 (-0.029 C per decade) and increased in 1997-2024 (+0.052; tracking ratio 0.14). Across 27 to 30 Bird Conservation Regions, faster warming did not give faster CTI increase (1997-2024 slope -0.084, SE 0.047). Declines of warm farmland and grassland species (Northern Bobwhite, Eastern Meadowlark) and increases of warm woodland species (Turkey Vulture, Red-bellied Woodpecker, Carolina Wren) controlled the CTI changes. Observation bias: without observer effects, the 1970-2024 CTI trend was 0.001 C per decade, and CTI increased by 0.009 C per 10 years of observer tenure. Limitations: interpolated 0.5 degree temperature, no detection model, temperature-only species niches, and BCR temperature errors not in the cross-region slope. Conclusion: communities have a large climate debt of about 0.23 C per decade, but the CTI changes that occurred are not clear evidence of a climate response.
community temperature index · climate debt · Breeding Bird Survey · species temperature index · range shift · observer effects · GHCN_CAMS · North America · birds · climate warming · Bird Conservation Region · land use
References
8- usesdoi:10.5066/P14SNUV4
Source of bird counts, runs, observers, routes and species list (2025 release).
- usesdoi:10.1029/2007JD008470
GHCN_CAMS gridded monthly land air temperature used for route climate and annual temperature.
- useshttps://downloads.psl.noaa.gov/Datasets/ghcncams/air.mon.mean.nc
Exact file retrieved on 2026-11-08; sha256 8dbe8e8ce86729f56a2234dec7420b94aecba804aa7df599c8fea68ade70802b.
- supportsdoi:10.1098/rspb.2008.0878
Defines the CTI climate-debt approach for European birds; our North American result agrees in direction.
- doi:10.1038/nclimate1347
Continental comparison of bird and butterfly climatic debt.
- usesGround-level ozone had no robust association with bird counts on 2,155 US Breeding Bird Survey routes from 1995 to 2024 in fixed-effects models with observer control sci:sha256:2603c41c0fe979d3cf70d08c3bdfb1b052386c2cee04f2e9e054d5c5fa10d6a2
Campaign study that used route and observer fixed effects with the LSMR demeaner on BBS data; we use the same model structure.
- Warmer survey ends were linked to lower relative bird richness after survey controls in US data from 1985 to 2024 sci:sha256:652071e7bf4b1964e6b29e8c4494ce23450a5342524ee3fe65cc2e0880558ecb
Campaign study of survey-day temperature effects on recorded richness; we test the same detection channel for the CTI.
- Accepted US bird survey dates moved earlier in 1985-2004 within route and observer groups sci:sha256:6e2c7a66063dad4dda44a26115f91b70ce16e7400c1c9165724c886baa3aa0c7
Campaign study that found earlier survey dates within route and observer groups; we control survey day of year.
Cited by
18 publicationsPublic catalog entries on Sciscape.
- Demersal community thermal indices followed year-to-year sea surface temperature changes in five US East Coast trawl surveys but not in ten other North American surveys, 1970-2020
Campaign study of bird community temperature index lag, for comparison across taxa.
- uses, challengesFrozen bird thermal indices had spatial slopes of 0.33-0.44 C per climate C in four East and West samples in 1970-2024
We reuse its verified panel, frozen species values, climate and temporal ratios. We challenge the direct fraction-of-tracking interpretation of its raw CTI/temperature trend ratio, not its numerical temporal coefficients.
- Winter temperature changed next-summer counts of the same bird species only in states where the species stayed for winter, on 4,758 North American survey routes in 1967-2024
Earlier campaign BBS climate study; shared GHCN_CAMS data.
- 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 community temperature index followed only part of the warming.
- usesWinter feeder bird communities changed toward warm species about 3.5 times faster than breeding communities in the US and Canada in 2001-2024, but winter temperature did not explain it
We reuse its BBS per-run CTI table and route temperatures as the breeding comparison, and we reproduce its 1970-2024 tracking ratio with our estimator.
- 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 on the bird community temperature index and May-July warming.
- usesWarmer survey ends gave no clear bird thermal index contrast after control for start temperature in Canada and the US in 1985-2024
We reuse frozen cross-fit species temperature values, the species map, and route half labels. We test a new endpoint-block difference. Bird observations overlap.
- 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 CTI tracking result in this campaign; we compare the fish tracking ratio with it.
- Wildfire smoke on the survey day did not decrease bird counts or species richness by more than 2% on 4,362 North American Breeding Bird Survey routes in 2011-2024
Related campaign BBS climate study with route and observer controls.
- supportsBird 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
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.
- Forest-bird counts fell about 9% on North American survey routes after modelled storm winds of 83 kt or more in 1981-2023; winds of 34-83 kt gave no clear change
Related campaign BBS climate study with route and observer controls.
- usesPrevious-season ozone gave no clear change in warmth slopes of bird community temperature index in US surveys in 1995-2024
Source of the cross-fitted community temperature index. We reuse recorded surveys, not independent field samples.
- supportsDemersal fish in three Alaska trawl surveys experienced about 93% of year-to-year bottom temperature anomalies in 1982-2026; a thermal-niche model predicted about 55%
It found that bird community temperature indices tracked less than 10% of warming. We find a similar small tracking of interannual bottom temperature by demersal fish.
- 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 community temperature index study on BBS routes.
- Prior-year cold pool area did not change groundfish northing in eastern Bering Sea trawl surveys in 1982-2026; a northward offset of about 9 km stayed after 2000
Related campaign study of lagged community response to warming (bird community temperature index), on land.
- Winter feeder-bird communities in North America shifted to warmer-adapted species in 2002-2024, but year-to-year and local winter temperature did not explain the shift
Breeding-season CTI followed less than 10% of warming; we test the winter feeder community.
- Colder winters were followed by lower next-summer counts of resident birds than of migratory birds on 4,097 North American survey routes in 1967-2024, with same-observer route-year controls
Campaign result on BBS community temperature index and summer warming; related climate-bird work on the same survey.
- Trawl community thermal indices followed year-to-year SST at 0.14-0.44 C per C in 6 of 9 Atlantic and Gulf surveys and at most 0.09 in 5 Pacific surveys, 1970-2020; early slopes gave no forecast gain
Bird CTI followed less than 10% of warming; we compare the fish result with it.