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

Northern Mockingbird Population Trend in Illinois

All statesGeneralists

Northern Mockingbird in Illinois has fallen sharply: down 51% on the route-weighted index since 1968.

-51%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 →
88Routes 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 Northern Mockingbird 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 →

Northern Mockingbird has fallen sharply in Illinois: down 50% on the route-weighted index since 1968.

Northern Mockingbird Population Forecast in Illinois

If the recent trend holds, Northern Mockingbird in Illinois is projected to fall about 42% by 2029 — from 2.3 in 2024 to a central estimate of 1.3 (95% range 0.00–4.1). A 5-year backtest shows a typical error of ±15.1%, with 100% of held-out values landing inside the 95% band.

-42%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 →
1.3Projected 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 →
0.00–4.195% 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 →
±15.1%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, Northern Mockingbird in Illinois is projected to fall about 42% by 2029 — from 2.3 in 2024 to a central estimate of 1.3 (95% range 0.00–4.1). A 5-year backtest shows a typical error of ±15.1%, with 100% 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 →
20251.60.004.4
20261.60.004.3
20271.50.004.3
20281.40.004.2
20291.30.004.1

Northern Mockingbird Survey Routes in Illinois

Routes recording Northern Mockingbird 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 →
Royalton2120242001
Columbia1520241966
Kell1520242001
Mt Vernon1220241971
Jamestown1020241966
Belknap920241970
Olney820241966
Bremen720241969
Delwood720241970
Cave In Rock720241993
Dudleyville720242001
Beaucoup620241971
Birds620241976
Marshall620242002
Karnak520242001
St Morgan420221967
Brnt Prairie420241976
Pulaski420231970
Beaverdam Lk420231970
York420241993
Eubanks420182001
Mascoutah Lk320241967
Darmstadt320241996
Sandusky320231993
Concord West320212001

Northern Mockingbird Population Trend in Other States

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

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