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

Cliff Swallow Population Trend in Illinois

All statesAerial insectivores

Cliff Swallow in Illinois has surged: up 170× on the route-weighted index since 1969.

170×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 →
97Routes 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 Cliff Swallow Trends in IllinoisNotable 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 increasecomputed 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 →

Cliff Swallow has surged in Illinois: up 170× on the route-weighted index since 1969.

Cliff Swallow Population Forecast in Illinois

If the recent trend holds, Cliff Swallow in Illinois is projected to stay roughly flat through 2030, near 16 (95% range 11–21). A 5-year backtest shows a typical error of ±21.6%, with 60% of held-out values landing inside the 95% band.

-10%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 →
16Projected 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 →
11–2195% 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 →
±21.6%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, Cliff Swallow in Illinois is projected to stay roughly flat through 2030, near 16 (95% range 11–21). A 5-year backtest shows a typical error of ±21.6%, with 60% of held-out values landing inside the 95% band.19672030
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 →
2026159.720
20271510.020
2028151021
2029161121
2030161121

Cliff Swallow Survey Routes in Illinois

Routes recording Cliff Swallow in Illinois.
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 →
Greenview17220252000
Sheffield8920241989
Holcomb8520251989
Mackinaw7720251999
Lake Galena7420212001
Beaverdam Lk6920231980
Deer Creek5520242003
Concord5520251991
Geneseo4720251969
Milford4720251972
Beaucoup4420251993
Caledonia4320251993
Eldred4020251993
Gulfport3820251997
Belleview3720251974
Monticello3520252003
Marshall3520252002
Pontiac3320251987
Fairland3320252000
Belknap3320251992
Atkinson3220241976
Buda3220231992
Pulaski3120252002
Guilford3020231977
Fairbury2620252002

Cliff Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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