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
Question: does local winter cold change the next breeding-season counts of resident birds, with migratory birds as a negative control? Data: North American Breeding Bird Survey 2025 release (6,870,825 route-species-year records, 368 species, 4,068 routes, 1970-2024), NOAA GHCN_CAMS monthly temperature, and the AVONET migration class (95 resident, 74 partial, 199 migratory species). Method: log(count+1) with species x route x observer and species x year fixed effects; December-February temperature anomaly from a route trend, with class-specific slopes; controls for spring and summer anomalies, survey weather, date and first observer year; two-way clustered intervals (space and year); plan written before model fits. Results: a winter 1 C warmer than the trend was followed by +0.81% (95% CI +0.48 to +1.15) resident counts, +0.55% (+0.26 to +0.85) partial-migrant counts and -0.00% (-0.23 to +0.23) migrant counts. The resident slope was positive with an interval above zero in East and West, 1970-1996 and 1997-2024. A year-relabel permutation test gave p = 0.002 for residents and p = 0.92 for migrants. An extreme cold winter (lowest 10%) gave -2.0% (-3.1 to -1.0) for residents and 0.0% for migrants. The resident slope was larger in the cold part of the species winter range (-0.24 per SD, -0.43 to -0.05). 74 of 95 resident species had positive slopes; Carolina Wren had the largest. Limitations: counts are an index without a detection model; seasonal mean temperature does not measure snow or short cold spells; AVONET gives one class per species; the next-winter placebo for residents was -0.26 (-0.57 to +0.04); migrants had a small positive slope in 1970-1996; the design is correlational. One SD of winter anomaly (1.7 C) changes resident counts by only about 1.4%.
Breeding Bird Survey · winter severity · extreme cold · resident birds · migratory birds · negative control · AVONET · GHCN_CAMS · fixed effects · climate change · population dynamics · North America
References
8- usesA 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 sci:sha256:3250b81c789d8cd041cf359eb978868b41ae06364686201fde41eeb105a326c8
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.
- 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 measurement of small northward bird range shifts on BBS routes.
- 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 community temperature index study on BBS routes.
- usesdoi:10.5066/P14SNUV4
North American Breeding Bird Survey 2025 data release.
- usesdoi:10.1029/2007JD008470
GHCN_CAMS gridded monthly land air temperature.
- usesdoi:10.1111/ele.13898
AVONET migration class and body mass.
- https://pubs.usgs.gov/publication/5224790
Link, Sauer and Niven 2008: seasonal components of avian population change with winter severity covariates.
- usesdoi:10.1198/jbes.2010.07136
Two-way cluster-robust inference.
Cited by
7 publicationsPublic catalog entries on Sciscape.
- Eastern Phoebe reports at severe-cold FeederWatch sites fell by half for three winters after Winter Storm Uri (2021); a general cold effect on small invertivores was not shown (US, Canada, 2002-2024)
BBS winter-anomaly effect on resident birds (monthly means).
- supports, reviewsWinter 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
Same resident slope (about 0.8% per C) with AVONET classes. We found a similar negative placebo but an uncertain western slope.
- reviewsWinter warmth was linked to changes between positive bird counts in eastern North America in 1967-2024, with uncertain western results
Prior resident and migrant winter count test motivates the mechanism check. It uses overlapping BBS records.
- supportsDaily cold nights added no information to the winter mean temperature for next-summer counts of winter-present birds on 4,571 North American routes in 1981-2025, but snow days and Winter Storm Uri did
Same DJF mean effect (about +1% per C) for resident birds.
- 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 study of winter weather and resident vs migrant BBS counts; we reuse its AVONET name fixes.
- Drought lowered bird counts in the dry central US plains again in 2006-2025, about 7-9% at SPI -3 (10.7% published); ten rain-tracking species gave half and the montane response did not repeat
Related campaign study of winter temperature and resident/migrant BBS counts.
- usesHurricane-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
We reuse and modify its BBS panel code, AVONET name mapping and fixed-effects estimator, and extend its resident-versus-migrant design from winter cold to hurricanes.