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

Grasshopper Sparrow Population Trend in New Jersey

All statesGrassland birds

Grasshopper Sparrow in New Jersey has fallen sharply: down 62% on the route-weighted index since 1969.

-62%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 →
29Routes 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 →
53YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Grasshopper Sparrow 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 declinecomputed 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 →

Grasshopper Sparrow has fallen sharply in New Jersey: down 62% on the route-weighted index since 1969.

Grasshopper Sparrow Population Forecast in New Jersey

If the recent trend holds, Grasshopper Sparrow in New Jersey is projected to fall about 17% by 2029 — from 0.19 in 2024 to a central estimate of 0.16 (95% range 0.00–0.45). A 5-year backtest shows a typical error of ±52.5%, with 100% of held-out values landing inside the 95% band.

-17%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 →
0.16Projected 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 →
0.00–0.4595% 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 →
±52.5%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, Grasshopper Sparrow in New Jersey is projected to fall about 17% by 2029 — from 0.19 in 2024 to a central estimate of 0.16 (95% range 0.00–0.45). A 5-year backtest shows a typical error of ±52.5%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.170.000.46
20260.160.000.46
20270.160.000.46
20280.160.000.45
20290.160.000.45

Grasshopper Sparrow Survey Routes in New Jersey

Routes recording Grasshopper Sparrow 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 →
Croton520071970
Woodbury Hgt320241967
Bloomsbury319911969
Roosevelt320071986
Deepwater219771971
Hope219771977
Pottersville220221977
Greenwich120221978
Six Points120191978
Toms River120051996
Albion119771968
Bennett Mill119761976
Sandbrook120231969
Holmansville119961981
Clarksville119761973
New Bedford119731970
Midvale119751975
Kemah Lake120051969
High Point119881988
Keyport119951990
Cranbury119971997
Friendship120182016
Pomona119901990
Mt Misery119891977
Pedricktown 2120172017

Grasshopper Sparrow Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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