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

Chestnut-sided Warbler Population Trend in New Jersey

All statesForest birds

Chestnut-sided Warbler in New Jersey has surged: up 91% on the route-weighted index since 1970.

+91%Since 1970TrendPercent 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 →
20Routes 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 →
56YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Chestnut-sided 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 →

Chestnut-sided Warbler has surged in New Jersey: up 91% on the route-weighted index since 1970.

Chestnut-sided Warbler Population Forecast in New Jersey

If the recent trend holds, Chestnut-sided Warbler in New Jersey is projected to rise about 68% by 2030 — from 0.22 in 2025 to a central estimate of 0.37 (95% range 0.00–0.76). A 5-year backtest shows a typical error of ±160.4%, with 100% of held-out values landing inside the 95% band.

+68%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 →
0.37Projected 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 →
0.00–0.7695% 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 →
±160.4%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, Chestnut-sided Warbler in New Jersey is projected to rise about 68% by 2030 — from 0.22 in 2025 to a central estimate of 0.37 (95% range 0.00–0.76). A 5-year backtest shows a typical error of ±160.4%, 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 →
20260.360.000.75
20270.370.000.75
20280.370.000.75
20290.370.000.75
20300.370.000.76

Chestnut-sided Warbler Survey Routes in New Jersey

Routes recording Chestnut-sided 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 →
Roosevelt520071990
High Point420251977
Toms River119661966
Sandbrook120051969
New Bedford119711971
Croton120071980
Robbinsville119771977
Hope119931978
Midvale119881970
Kemah Lake120151975
Bloomsbury119911991
Dover120221978
Pottersville120181980
Gillette120241997
Keyport120022002
Cranbury119871987
Friendship119821982
Pedricktown119981997
Croton 2120232008
Ramseysburg120162010

Chestnut-sided Warbler Population Trend in Other States

alabamaarkansascoloradoconnecticutgeorgiaillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotanevadanew-hampshirenew-yorknorth-carolinanorth-dakotaohiopennsylvaniarhode-islandtennesseevermontvirginiawest-virginiawisconsinwyoming

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