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

Swamp Sparrow Population Trend in New Jersey

All statesGeneralists

Swamp Sparrow in New Jersey has collapsed: down 80% on the route-weighted index since 1968.

-80%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 →
16Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Swamp 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 →

Swamp Sparrow has collapsed in New Jersey: down 80% on the route-weighted index since 1968.

Swamp Sparrow Population Forecast in New Jersey

If the recent trend holds, Swamp Sparrow in New Jersey is projected to rise about 127% by 2029 — from 0.10 in 2024 to a central estimate of 0.22 (95% range 0.00–0.54). A 5-year backtest shows a typical error of ±137.2%, with 100% of held-out values landing inside the 95% band.

+127%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 →
0.22Projected 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 →
0.00–0.5495% 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 →
±137.2%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, Swamp Sparrow in New Jersey is projected to rise about 127% by 2029 — from 0.10 in 2024 to a central estimate of 0.22 (95% range 0.00–0.54). A 5-year backtest shows a typical error of ±137.2%, 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 →
20250.230.000.55
20260.230.000.55
20270.220.000.55
20280.220.000.54
20290.220.000.54

Swamp Sparrow Survey Routes in New Jersey

Routes recording Swamp 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 →
Spraguetown219841977
Hope219901972
High Point220221977
Pomona220011978
Greenwich119881967
Six Points119901983
Deepwater119771969
Masonville119701966
New Bedford119781978
Midvale120061972
Kemah Lake120241986
Ramseysburg120121995
Dover120231977
Gillette120241988
Roosevelt119951986
Friendship120191977

Swamp Sparrow Population Trend in Other States

connecticutdelawareillinoisindianaiowamainemarylandmassachusettsmichiganminnesotanebraskanew-hampshirenew-yorknorth-dakotaohiopennsylvaniarhode-islandsouth-dakotavermontvirginiawest-virginiawisconsin

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