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

Vesper Sparrow Population Trend in New Jersey

All statesGrassland birds

Vesper Sparrow in New Jersey has fallen sharply: down 67% on the route-weighted index since 1968.

-67%Since 1968TrendPercent 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 →
11Routes 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 →
24YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Vesper 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 →

Vesper Sparrow has fallen sharply in New Jersey: down 67% on the route-weighted index since 1968.

Vesper Sparrow Population Forecast in New Jersey

If the recent trend holds, Vesper Sparrow in New Jersey is projected to fall about 89% by 2007 — from 0.05 in 2002 to a central estimate of 0.01 (95% range 0.00–0.17). A 5-year backtest shows a typical error of ±55.6%, with 100% of held-out values landing inside the 95% band.

-89%Change by 2007TrendPercent 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 →
0.01Projected 2007 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.1795% 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 →
±55.6%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, Vesper Sparrow in New Jersey is projected to fall about 89% by 2007 — from 0.05 in 2002 to a central estimate of 0.01 (95% range 0.00–0.17). A 5-year backtest shows a typical error of ±55.6%, with 100% of held-out values landing inside the 95% band.19662007
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 →
20030.020.000.18
20040.020.000.18
20050.010.000.17
20060.010.000.17
20070.010.000.17

Vesper Sparrow Survey Routes in New Jersey

Routes recording Vesper 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 →
Sandbrook219691969
Six Points119781978
Ancora119701968
Masonville119671966
Bennett Mill119721968
New Bedford120021970
Robbinsville119691968
Bloomsbury119951969
High Point120011988
Pottersville119801980
Roosevelt119941994

Vesper Sparrow Population Trend in Other States

arizonacaliforniacoloradoconnecticutdelawareidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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