BirdAnalyst
Species · New Jersey · BBS 2026 Release · 1966–2025

Field Sparrow Population Trend in New Jersey

All statesForest birds

Field Sparrow in New Jersey has fallen sharply: down 65% on the route-weighted index since 1968.

-65%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 →
42Routes 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 →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Field 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 →

Field Sparrow has fallen sharply in New Jersey: down 65% on the route-weighted index since 1968.

Field Sparrow Population Forecast in New Jersey

If the recent trend holds, Field Sparrow in New Jersey is projected to fall about 61% by 2030 — from 3.9 in 2025 to a central estimate of 1.5 (95% range 0.00–4.6). A 5-year backtest shows a typical error of ±46.6%, with 100% of held-out values landing inside the 95% band.

-61%Change by 2030TrendPercent 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 →
1.5Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–4.695% 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 →
±46.6%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, Field Sparrow in New Jersey is projected to fall about 61% by 2030 — from 3.9 in 2025 to a central estimate of 1.5 (95% range 0.00–4.6). A 5-year backtest shows a typical error of ±46.6%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20261.90.004.9
20271.80.004.8
20281.70.004.7
20291.60.004.6
20301.50.004.6

Field Sparrow Survey Routes in New Jersey

Routes recording Field 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 →
Croton1720071970
Pedricktown 21520252013
Croton 21320252008
Hope1119941970
Pedricktown1020121991
Holmansville920091969
Villas919811979
Ramseysburg920251995
Deepwater819771969
Sandbrook820251969
Gillette620251988
Spraguetown 2420072000
Mt Misery419881976
Toms River320241966
Ancora319771966
Masonville319701966
Kemah Lake320241966
Bloomsbury320241969
High Point320251977
Cape May Ch320131992
Woodbury Hgt220251967
Six Points220251978
Clarksville219911969
Robbinsville219791966
Dover220231977

Field Sparrow Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.