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

Summer Tanager Population Trend in Illinois

All statesForest birds

Summer Tanager in Illinois has surged: up 28× on the route-weighted index since 1969.

28×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 →
57Routes 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 Summer Tanager 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 →

Summer Tanager has surged in Illinois: up 28× on the route-weighted index since 1969.

Summer Tanager Population Forecast in Illinois

If the recent trend holds, Summer Tanager in Illinois is projected to rise about 16% by 2030 — from 1.2 in 2025 to a central estimate of 1.4 (95% range 0.95–1.8). A 5-year backtest shows a typical error of ±20.3%, with 60% of held-out values landing inside the 95% band.

+16%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 →
1.4Projected 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 →
0.95–1.895% 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 →
±20.3%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, Summer Tanager in Illinois is projected to rise about 16% by 2030 — from 1.2 in 2025 to a central estimate of 1.4 (95% range 0.95–1.8). A 5-year backtest shows a typical error of ±20.3%, with 60% 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 →
20261.30.861.7
20271.30.891.7
20281.30.911.7
20291.30.931.8
20301.40.951.8

Summer Tanager Survey Routes in Illinois

Routes recording Summer Tanager 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 →
Sandusky1420231993
Bremen1320251970
Beaverdam Lk1320231970
Cave In Rock1320241993
Royalton1220252001
Belknap920251970
Belleview820251966
Eldred620251993
Pulaski520251971
St Morgan420221969
Mt Vernon420251975
Delwood420251970
Athens320252008
Terre Haute320092009
Martinsville320121970
Camp Point320252009
Grape Creek220242003
Columbia220251968
Mascoutah Lk220251979
Eubanks220242008
Marshall220252010
Kell220252002
Karnak220252001
York220252011
Atkinson120162016

Summer Tanager Population Trend in Other States

alabamaarizonaarkansascaliforniadelawarefloridageorgiaindianaiowakansaskentuckylouisianamarylandmississippimissourinebraskanevadanew-jerseynew-mexiconorth-carolinaohiooklahomapennsylvaniasouth-carolinatennesseetexasutahvirginiawest-virginiawisconsin

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