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

Chimney Swift Population Trend in Iowa

All statesAerial insectivores

Chimney Swift in Iowa has collapsed: down 88% on the route-weighted index since 1969.

-88%Since 1969TrendPercent 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 →
39Routes 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 →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

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

long arc declinecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Chimney Swift has collapsed in Iowa: down 87% on the route-weighted index since 1969.

Chimney Swift Population Forecast in Iowa

If the recent trend holds, Chimney Swift in Iowa is projected to fall about 100% by 2029 — from 1.2 in 2024 to a central estimate of 0.00 (95% range 0.00–2.7). A 5-year backtest shows a typical error of ±28.7%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–2.795% 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 →
±28.7%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, Chimney Swift in Iowa is projected to fall about 100% by 2029 — from 1.2 in 2024 to a central estimate of 0.00 (95% range 0.00–2.7). A 5-year backtest shows a typical error of ±28.7%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.620.003.3
20260.460.003.2
20270.300.003.0
20280.140.002.8
20290.000.002.7

Chimney Swift Survey Routes in Iowa

Routes recording Chimney Swift in Iowa.
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 →
Desmoines3319791968
Cedar Valley1519971967
Bryant1020241967
Sioux City820241968
West Liberty620231968
Washta620141968
Brooklyn520181967
Maquoketa520231967
Prairieburg420151968
Scranton420101967
Clare420191973
Gaza420181969
Rock Valley420241968
Panther320231967
Alice319961967
Hudson320221967
Dinsdale320051968
Williamsburg220191967
Davis Corner220181968
Burchinal220151999
College Spgs 2220182005
Tipton220211993
Mccallsburg220241996
Mt Hamill120241967
Exline120231974

Chimney Swift Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.