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

Blue Grosbeak Population Trend in New Jersey

All statesGeneralists

Blue Grosbeak in New Jersey has surged: up 142% on the route-weighted index since 1969.

+142%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 →
22Routes 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 →
54YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Blue Grosbeak 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 →

Blue Grosbeak has surged in New Jersey: up 142% on the route-weighted index since 1969.

Blue Grosbeak Population Forecast in New Jersey

If the recent trend holds, Blue Grosbeak in New Jersey is projected to fall about 16% by 2029 — from 0.81 in 2024 to a central estimate of 0.68 (95% range 0.22–1.1). A 5-year backtest shows a typical error of ±22.5%, with 100% of held-out values landing inside the 95% band.

-16%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 →
0.68Projected 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 →
0.22–1.195% 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 →
±22.5%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, Blue Grosbeak in New Jersey is projected to fall about 16% by 2029 — from 0.81 in 2024 to a central estimate of 0.68 (95% range 0.22–1.1). A 5-year backtest shows a typical error of ±22.5%, 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 →
20250.650.191.1
20260.660.201.1
20270.670.201.1
20280.680.211.1
20290.680.221.1

Blue Grosbeak Survey Routes in New Jersey

Routes recording Blue Grosbeak 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 →
New Bedford820021991
Woodbury Hgt620241968
Pedricktown 2520242013
Pedricktown320121991
Greenwich220241966
Six Points220221979
Deepwater219761976
Del Haven219911991
Cape May Ch220131993
Bennett Mill 2220242016
Albion119901978
Spraguetown 2120022002
Sandbrook119801980
Holmansville119961990
Clarksville119841984
Keyport119951992
Cranbury119961988
Roosevelt120131986
Friendship120242015
Pomona120231979
Spraguetown119911991
Winslow120241990

Blue Grosbeak Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamarylandminnesotamississippimissourimontananebraskanevadanew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvirginiawest-virginiawyoming

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