BirdAnalyst
Species · Wisconsin · BBS 2025 Release · 1966–2024

Tree Swallow Population Trend in Wisconsin

All statesAerial insectivores

Tree Swallow in Wisconsin has declined: down 30% on the route-weighted index since 1968.

-30%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 →
58YearsYears 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 78% by 2029 — from 4.5 in 2024 to a central estimate of 7.9 (95% range 2.2–14). A 5-year backtest shows a typical error of ±114%, with 40% of held-out values landing inside the 95% band.

+78%Change by 2029TrendPercent 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 →
7.9Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
2.2–1495% 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 →
±114%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 78% by 2029 — from 4.5 in 2024 to a central estimate of 7.9 (95% range 2.2–14). A 5-year backtest shows a typical error of ±114%, with 40% of held-out values landing inside the 95% band.19662029
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 →
20258.22.414
20268.12.414
20278.12.314
20288.02.314
20297.92.214

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
Holland3420241998
Verona2120241991
Brownsville2020241974
Omro 21820242002
Mather1720231966
Briggsville1620241999
Iron River1520241967
Bayfield1520241967
Holway1219891967
Stevens Pt1120231966
Flambeau1120241998
Couderay1020191969
Phillips1020241966
Princeton1020241966
Fall River1020241966
Eden1020241967
Grimms1020211998
Kiel1020221998
Dresser920241966
Hatfield919981970
Elderon920231966
Rolling Pr920241972
Union Twp820241968
Rib Lake820241966

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 2026-05-22.