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

Pied-billed Grebe Population Trend in Illinois

All statesWetland birds

Pied-billed Grebe in Illinois has collapsed: down 77% on the route-weighted index since 1970.

-77%Since 1970TrendPercent 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 →
15Routes 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 →
26YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Pied-billed Grebe 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 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 →

Pied-billed Grebe has collapsed in Illinois: down 77% on the route-weighted index since 1970.

Pied-billed Grebe Population Forecast in Illinois

If the recent trend holds, Pied-billed Grebe in Illinois is projected to stay roughly flat through 2030, near 0.00 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±281.1%, with 80% of held-out values landing inside the 95% band.

n/aChange 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 →
0.00Projected 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 →
0.00–0.0995% 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 →
±281.1%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, Pied-billed Grebe in Illinois is projected to stay roughly flat through 2030, near 0.00 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±281.1%, with 80% of held-out values landing inside the 95% band.19682030
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 →
20260.000.000.09
20270.000.000.09
20280.000.000.09
20290.000.000.09
20300.000.000.09

Pied-billed Grebe Survey Routes in Illinois

Routes recording Pied-billed Grebe 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 →
Troy Grove220021995
Chandlervill219861976
Minonk220102010
Itasca120002000
Belleview119991976
Geneseo120251968
Sheffield119701970
Bradbury120252025
New Lenox119821968
Clayton120252025
Brnt Prairie120092009
Mt Vernon119821982
Olney120132013
Grape Creek120182018
Pulaski119951987

Pied-billed Grebe Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwisconsinwyoming

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