BirdAnalyst
Species · New Jersey · BBS 2025 Release · 1966–2024

Cerulean Warbler Population Trend in New Jersey

All statesForest birds

Cerulean Warbler in New Jersey has surged: up 222% on the route-weighted index since 1980.

+222%Since 1980TrendPercent 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 →
5Routes 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 →
35YearsYears 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 New JerseyNotable 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 →

Cerulean Warbler has surged in New Jersey: up 222% on the route-weighted index since 1980.

Cerulean Warbler Population Forecast in New Jersey

If the recent trend holds, Cerulean Warbler in New Jersey is projected to rise about 98% by 2029 — from 0.10 in 2024 to a central estimate of 0.19 (95% range 0.03–0.34). A 5-year backtest shows a typical error of ±47.1%, with 80% of held-out values landing inside the 95% band.

+98%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 →
0.19Projected 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 →
0.03–0.3495% 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 →
±47.1%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, Cerulean Warbler in New Jersey is projected to rise about 98% by 2029 — from 0.10 in 2024 to a central estimate of 0.19 (95% range 0.03–0.34). A 5-year backtest shows a typical error of ±47.1%, with 80% of held-out values landing inside the 95% band.19782029
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 →
20250.180.020.34
20260.180.030.34
20270.180.030.34
20280.190.030.34
20290.190.030.34

Cerulean Warbler Survey Routes in New Jersey

Routes recording Cerulean Warbler in New Jersey.
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 →
Kemah Lake320141991
High Point220241988
Midvale119791979
Bloomsbury119781978
Dover119801980

Cerulean Warbler Population Trend in Other States

alabamaarkansasconnecticutgeorgiaillinoisindianakentuckylouisianamarylandmassachusettsmichiganminnesotamississippimissourinew-hampshirenew-yorknorth-carolinaohiooklahomapennsylvaniatennesseevermontvirginiawest-virginiawisconsin

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