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

Purple Martin Population Trend in Illinois

All statesAerial insectivores

Purple Martin in Illinois has declined: down 38% on the route-weighted index since 1968.

-38%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 →
100Routes 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 Purple Martin 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 →

No notable trend signals for Purple Martin in Illinois. See the full index history below.

Purple Martin Population Forecast in Illinois

If the recent trend holds, Purple Martin in Illinois is projected to fall about 59% by 2030 — from 5.3 in 2025 to a central estimate of 2.2 (95% range 0.00–5.2). A 5-year backtest shows a typical error of ±65.3%, with 40% of held-out values landing inside the 95% band.

-59%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 →
2.2Projected 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 →
0.00–5.295% 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 →
±65.3%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, Purple Martin in Illinois is projected to fall about 59% by 2030 — from 5.3 in 2025 to a central estimate of 2.2 (95% range 0.00–5.2). A 5-year backtest shows a typical error of ±65.3%, with 40% 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 →
20262.40.005.4
20272.30.005.4
20282.30.005.3
20292.20.005.3
20302.20.005.2

Purple Martin Survey Routes in Illinois

Routes recording Purple Martin 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 →
Bradbury2820251970
Delwood2820251970
Eubanks2620252001
Athensville2420251971
Seneca2220252009
Bremen2120251969
Robinson1820231970
Janesville1620251976
Birds1520241976
Camp Point1520251994
Sherburnvill1420231967
Pulaski1420251970
Belknap1420251970
York1420251993
Sheffield1220241966
Le Roy1220241993
Humboldt1120251972
Karnak1120252001
Belleview1020251966
Martinsville1020251970
Mt Vernon1020251976
Terre Haute920241966
Beaucoup920251971
Dudleyville920252005
Columbia820251966

Purple Martin Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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