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

Black Vulture Population Trend in Illinois

All statesGeneralists

Black Vulture in Illinois has surged: up 112% on the route-weighted index since 1978.

+112%Since 1978TrendPercent 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 →
12Routes 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 →
38YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black Vulture 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 →

Black Vulture has surged in Illinois: up 112% on the route-weighted index since 1978.

Black Vulture Population Forecast in Illinois

If the recent trend holds, Black Vulture in Illinois is projected to rise about 35% by 2029 — from 0.19 in 2024 to a central estimate of 0.25 (95% range 0.09–0.41). A 5-year backtest shows a typical error of ±40.5%, with 100% of held-out values landing inside the 95% band.

+35%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 →
0.25Projected 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 →
0.09–0.4195% 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 →
±40.5%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, Black Vulture in Illinois is projected to rise about 35% by 2029 — from 0.19 in 2024 to a central estimate of 0.25 (95% range 0.09–0.41). A 5-year backtest shows a typical error of ±40.5%, with 100% of held-out values landing inside the 95% band.19752029
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 →
20250.230.070.39
20260.240.080.40
20270.240.080.40
20280.250.090.41
20290.250.090.41

Black Vulture Survey Routes in Illinois

Routes recording Black Vulture 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 →
Beaverdam Lk720231993
Belknap520241975
Karnak420242003
Sandusky320181999
Columbia220242024
Pulaski220181986
Royalton120232023
Brownville120242024
Cave In Rock120241998
Dudleyville120212021
Bremen120242013
Delwood120221982

Black Vulture Population Trend in Other States

alabamaarizonaarkansasconnecticutdelawarefloridageorgiaindianakentuckylouisianamarylandmassachusettsmississippimissourinew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniasouth-carolinatennesseetexasvermontvirginiawest-virginia

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