BirdAnalyst
Species · Massachusetts · BBS 2025 Release · 1966–2024

Swamp Sparrow Population Trend in Massachusetts

All statesGeneralists

Swamp Sparrow in Massachusetts has surged: up 87% on the route-weighted index since 1968.

+87%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 →
24Routes 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 →
58YearsYears 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 MassachusettsNotable 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 →

Swamp Sparrow has surged in Massachusetts: up 87% on the route-weighted index since 1968.

Swamp Sparrow Population Forecast in Massachusetts

If the recent trend holds, Swamp Sparrow in Massachusetts is projected to fall about 14% by 2029 — from 1.1 in 2024 to a central estimate of 0.98 (95% range 0.43–1.5). A 5-year backtest shows a typical error of ±23.4%, with 100% of held-out values landing inside the 95% band.

-14%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 →
0.98Projected 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 →
0.43–1.595% 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 →
±23.4%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, Swamp Sparrow in Massachusetts is projected to fall about 14% by 2029 — from 1.1 in 2024 to a central estimate of 0.98 (95% range 0.43–1.5). A 5-year backtest shows a typical error of ±23.4%, 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 →
20250.970.421.5
20260.970.431.5
20270.970.431.5
20280.970.431.5
20290.980.431.5

Swamp Sparrow Survey Routes in Massachusetts

Routes recording Swamp Sparrow in Massachusetts.
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 →
N. Andover520241995
Chesterfield420241967
Pittsfield420161974
Warren320091968
Sheffield320131969
Monterey320242019
Cummington 2320192015
Ware River220221993
Brockton220191971
E Pepperell219931966
N Orange220241969
Warren 2220242010
Marion120232023
Prattville119981998
Newburyport120221967
Maynard120221967
Littleton120241968
N Oxford120071971
Princeton119741974
Belchertown120211967
S Barre120221968
Cummington120031981
Cheshire119941970
Holden120091977

Swamp Sparrow Population Trend in Other States

connecticutdelawareillinoisindianaiowamainemarylandmichiganminnesotanebraskanew-hampshirenew-jerseynew-yorknorth-dakotaohiopennsylvaniarhode-islandsouth-dakotavermontvirginiawest-virginiawisconsin

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