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

Cerulean Warbler Population Trend in Illinois

All statesForest birds

Cerulean Warbler in Illinois has declined: down 41% on the route-weighted index since 1973.

-41%Since 1973TrendPercent 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 →
13Routes 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 →
16YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Cerulean Warbler 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 Cerulean Warbler in Illinois. See the full index history below.

Cerulean Warbler Survey Routes in Illinois

Routes recording Cerulean Warbler 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 →
Athensville119731973
Belleview120231969
York120232023
Sandusky120212021
Cave In Rock120092009
Mascoutah Lk119911988
St Morgan120212021
Olney119841969
Flora119791979
Birds120242023
Bremen119861972
Delwood119861986
Beaverdam Lk119771977

Cerulean Warbler Population Trend in Other States

alabamaarkansasconnecticutgeorgiaindianakentuckylouisianamarylandmassachusettsmichiganminnesotamississippimissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniatennesseevermontvirginiawest-virginiawisconsin

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