BirdAnalyst
Species · Massachusetts · BBS 2026 Release · 1966–2025

Marsh Wren Population Trend in Massachusetts

All statesForest birds

Marsh Wren in Massachusetts has surged: up 209% on the route-weighted index since 1970.

+209%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 →
6Routes 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 →
43YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Marsh Wren 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 →

Marsh Wren has surged in Massachusetts: up 209% on the route-weighted index since 1970.

Marsh Wren Population Forecast in Massachusetts

If the recent trend holds, Marsh Wren in Massachusetts is projected to rise about 587% by 2030 — from 0.06 in 2025 to a central estimate of 0.43 (95% range 0.06–0.79). A 5-year backtest shows a typical error of ±257.3%, with 40% of held-out values landing inside the 95% band.

+587%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 →
0.43Projected 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 →
0.06–0.7995% 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 →
±257.3%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, Marsh Wren in Massachusetts is projected to rise about 587% by 2030 — from 0.06 in 2025 to a central estimate of 0.43 (95% range 0.06–0.79). A 5-year backtest shows a typical error of ±257.3%, with 40% of held-out values landing inside the 95% band.19672030
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 →
20260.410.040.77
20270.410.050.77
20280.420.050.78
20290.420.060.78
20300.430.060.79

Marsh Wren Survey Routes in Massachusetts

Routes recording Marsh Wren 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 →
Newburyport1220221967
Brockton219871976
Mansfield119701970
N. Andover120252007
Warren 2120212021
Sheffield120132013

Marsh Wren Population Trend in Other States

alabamaarizonacaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamainemarylandmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatexasutahvermontvirginiawashingtonwisconsinwyoming

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