BirdAnalyst
Species · Wisconsin · BBS 2026 Release · 1966–2025

Tree Swallow Population Trend in Wisconsin

All statesAerial insectivores

Tree Swallow in Wisconsin has declined: down 32% on the route-weighted index since 1968.

-32%Since 1968TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
98Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Tree Swallow Trends in WisconsinNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Tree Swallow in Wisconsin. See the full index history below.

Tree Swallow Population Forecast in Wisconsin

If the recent trend holds, Tree Swallow in Wisconsin is projected to rise about 83% by 2030 — from 4.1 in 2025 to a central estimate of 7.6 (95% range 1.8–13). A 5-year backtest shows a typical error of ±108.1%, with 100% of held-out values landing inside the 95% band.

+83%Change by 2030TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
7.6Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
1.8–1395% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±108.1%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Tree Swallow in Wisconsin is projected to rise about 83% by 2030 — from 4.1 in 2025 to a central estimate of 7.6 (95% range 1.8–13). A 5-year backtest shows a typical error of ±108.1%, with 100% of held-out values landing inside the 95% band.19662030
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20267.82.014
20277.82.014
20287.71.913
20297.61.813
20307.61.813

Tree Swallow Survey Routes in Wisconsin

Routes recording Tree Swallow in Wisconsin.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Omro3720011966
Iron River3120251967
Mather1720231966
Holland1320251998
Holway1219891967
Omro 21220252002
Verona1220251991
Briggsville1220251999
Loraine1120251966
Gilman1120251966
Stevens Pt1120231966
Brownsville1120251974
Kiel1120251998
Couderay1020191969
Phillips1020251966
Princeton1020241966
Hebron1020251971
Flambeau1020251998
Grimms1020211998
Hatfield919981970
Elderon920231966
Clintonville920251967
Bayfield820251967
Wis Rapids820231966
Casco820251966

Tree Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.