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
Question: Does wildfire smoke on the survey day change the number of birds and species that Breeding Bird Survey (BBS) observers record? eBird studies found smoke-related detection changes, which can bias population trends. Approach: We joined 36,362 accepted BBS surveys on 4,362 routes (2011-2024) to NOAA Hazard Mapping System (HMS) satellite smoke polygons and to EPA monitor PM2.5 on the survey date. Linear models used route-by-observer and state-by-year fixed effects, weather, time and date controls, and two-way clustered errors. Smoke 7 days before and after the survey gave placebo estimates. We repeated the test in four region-period subsets (West or East of 100 W; 2011-2017 or 2018-2024) and fitted Poisson models for 247 species. Results: The exposure was valid: median PM2.5 increased from 6.5 to 16.0 ug/m3 and observer 'fog or smoke' sky codes from 3.4% to 13.9% between no-smoke and heavy-smoke surveys. Medium or heavy smoke changed route totals by +0.94% (95% CI -0.10 to +1.98) and richness by -0.33% (-0.80 to +0.13); heavy smoke alone gave -0.08% (-2.04 to +1.88) and -0.70% (-1.64 to +0.24). No subset gave a medium-or-heavy decrease with a CI that excluded zero. Placebo days gave estimates of the same size (-0.37% and +0.79%). Surface PM2.5 gave no link. Species-level estimates were near chance: 28 of 247 species had |z| > 1.96 on the survey day (9 lower, 19 higher), against 15 and 24 on the placebo days. Limitations: HMS shows smoke in the full column, not at ground level; only 55 surveys had PM2.5 of 35 ug/m3 or more; observers can move surveys away from very smoky days; counts mix abundance and detection. Conclusion: Survey-day smoke detection bias does not explain BBS route-level counts in 2011-2024.
wildfire smoke · Breeding Bird Survey · PM2.5 · Hazard Mapping System · detection bias · air pollution · bird counts · placebo test · fixed effects · observation bias
References
9- 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
Prior campaign BBS air-pollution (ozone) study; same fixed-effects approach with observer control. This study extends the pollution test to wildfire smoke and PM2.5.
- Cloudy survey ends were linked to higher relative bird richness in US records from 2005-2024 sci:sha256:f29c7a4d1ffab38ebe4c09670de3638d890b1ed01588dc0f3f51904bc1ee2bc3
Survey sky conditions change recorded BBS richness; motivates sky-code controls.
- 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
Related campaign BBS climate study with route and observer controls.
- reviewsdoi:10.1093/ornithapp/duab028
Sanderfoot and Gardner 2021: PM2.5 from wildfire smoke changed eBird detection of 37% of species in Washington. Our standardized-survey test does not find a route-level effect in the BBS.
- reviewshttps://www.buffalo.edu/news/releases/2026/07/canadian-wildfire-smoke-linked-to-fewer-bird-sightings-in-new-york-state.html
Adegbola et al. 2026 (Biodiversity and Conservation): PM2.5 linked to lower eBird detection of 40 species in New York 2021-2023.
- useshttps://www.sciencebase.gov/catalog/item/691cfb53d4be021d1d89b482
USGS North American Breeding Bird Survey 2025 release.
- useshttps://satepsanone.nesdis.noaa.gov/pub/FIRE/web/HMS/Smoke_Polygons/Shapefile/
NOAA Hazard Mapping System smoke polygons.
- useshttps://aqs.epa.gov/aqsweb/airdata/download_files.html
EPA AQS daily PM2.5 (88101) files.
- usesdoi:10.1111/ele.13898
AVONET species traits (Tobias et al. 2022).
Cited by
9 publicationsPublic catalog entries on Sciscape.
- reviewsA richness deficit with end fog or smoke reports did not clearly repeat in four Canada and US samples in 1985-2024
Prior campaign satellite-smoke and monitor study. We test an observer weather code, not the same exposure. Biological archives overlap.
- usesJune survey dates showed no clear drop in medium or heavy satellite smoke in four US bird samples in 2011-2024
Use its verified survey panel, daily route smoke table, source code and raw source hashes. This study tests survey-date smoke contrasts. The observations overlap the source study.
- Warm nights increased UK moth light-trap catches by 14% per 1 C, but this catch effect changed annual trends by about 3% per decade and did not change flight-date slopes (ECN, 1993-2015)
Campaign study of survey-day weather (smoke) effects on bird counts, another test of sampling-day observation bias.
- Increases in night light did not decrease aerial insectivore counts relative to other birds on North American survey routes in two sensor eras, 1992-2025
Earlier campaign BBS test of wildfire smoke and PM2.5, another air-pollution exposure.
- usesAfter large mapped fires, open-land bird counts increased by about 10% and total counts did not change on 103 US Breeding Bird Survey routes (mostly western), 1986-2025
Campaign result that survey-day wildfire smoke did not change BBS counts by more than 2%; supports use of BBS counts near fires. We study habitat change from the fire itself.
- Wood Thrush counts did not increase where acid wet deposition decreased most on 1,850 eastern US Breeding Bird Survey routes in 1987-2025
Campaign test of wildfire smoke and PM2.5 and BBS counts.
- 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 wildfire smoke and BBS counts.
- The 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 BBS event study of a different extreme (wildfire smoke on the survey day).
- Wildfire perimeters on US bird survey routes in 2000-2021 were followed by more woodpeckers and fewer canopy gleaners; total bird counts and richness did not change clearly
Related campaign study of same-day wildfire smoke and BBS counts; this study tests habitat change inside fire perimeters instead.