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
Question: does the relation between breeding-season warmth and bird counts depend on the position of a route in the thermal range of each species? Climate-niche theory predicts better results after a warm season in the cool part of a range and worse results in the warm part. Data: North American Breeding Bird Survey 2025 release (1970-2024; 6,870,825 route-species-year records; 368 species; 4,068 routes) and NOAA GHCN_CAMS May-July temperature. Method: thermal niche position (TNP) is the route 1971-2000 climate as a standard score in the abundance-weighted range of the species. We modelled log(count + 1) with species x route x observer and species x year fixed effects, the detrended anomaly of the previous and the same season, their TNP interactions, and survey-weather and date controls. Intervals are two-way clustered by spatial block and year. The plan was written before the fits. Result: the previous-season anomaly x TNP interaction was -0.42 (95% interval -0.57 to -0.27) in 100 x log-count units per 1 C per SD. The previous-season slope was +0.76 in the coolest TNP quintile and -0.57 in the warmest. The interaction was negative in all four East/West x 1970-1996/1997-2024 subsets (three intervals exclude zero), in the latitude part (-0.61) and the non-latitude part (-0.23) of TNP, and after a year-relabel permutation test. A placebo with the next-season anomaly gave +0.05 (-0.16 to 0.26). 63% of species had negative estimates. Limitations: no detection model, coarse 0.5 degree temperature, a range truncated by the survey network, a small effect of about 1% per C, and a correlational design. The year-to-year response does not prove a long-term trend response.
thermal niche position · range position · Breeding Bird Survey · temperature anomaly · lagged response · climate change · range shift mechanism · observer effects · two-way clustering · placebo test · permutation test · North America · birds · GHCN_CAMS
References
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North American Breeding Bird Survey 2025 release: counts, survey weather, routes and species list.
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ScienceBase item of the BBS 2025 release.
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GHCN_CAMS monthly air temperature file used for route May-July temperature.
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Description of the GHCN_CAMS temperature analysis.
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Two-way cluster-robust variance estimator.
- 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 sci:sha256:7714830c552415458e0fbece8fb93ae05d88d18000b801144071d2993a034a3e
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.
- 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 sci:sha256:c0a3a9aa7b4c6115119528bcd43c4f51b7bc2de204c571e3c468161b72cf1b91
Prior campaign result on the bird community temperature index and May-July warming.
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Prior campaign test of previous-season temperature and next-year counts at the community level; this study tests species-specific responses by thermal position.
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Global meta-analysis of range shifts under warming.
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Community temperature index and lag of bird communities behind warming.
Cited by
8 publicationsPublic catalog entries on Sciscape.
- 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 study of breeding-season warmth and next-year BBS counts.
- 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 breeding-season warmth and next-year BBS counts; we test the winter season and the migratory guild instead.
- usesWarmer 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
We reuse and modify its BBS panel code and exact two-way fixed-effects estimator, and we test the winter weather and migration strategy that it lists as untested.
- uses, reviewsA prior warmth by thermal niche position term stayed negative with route-year effects in pooled North American bird counts, 1970-2024
We rebuild its public panel and base model. We add route-year effects, four sample checks, a full first-year exclusion, and a compact offline panel.
- Estimates for prior warm, dry summers changed sign between two abundance measures for nine butterflies in Britain in 1980-2024
Related campaign test of lagged warmth in North American birds. We use separate data and do not test its thermal-niche mechanism.
- 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 breeding-season warmth and next-year BBS counts; this study tests the preceding winter with a different design.
- usesThe June 2021 heat dome gave no clear bird-count decrease on 701 western survey routes in 2022-2025; acute heat in 1981-2025 gave about 1% lower next-year richness and no count change
Prior campaign study of seasonal-mean breeding-season warmth and next-year BBS counts; we use a similar fixed-effects design and add acute peak heat and the 2021 heat dome.
- Hurricane-force winds gave at most a small decrease in next-summer resident bird counts on 2,025 eastern US survey routes in 1970-2024, and the decrease did not repeat across regions and periods
Prior campaign BBS study of warm breeding seasons and next-year counts.