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Species · Connecticut · BBS 2025 Release · 1966–2024

Marsh Wren Population Trend in Connecticut

All statesForest birds

Marsh Wren in Connecticut has surged: up 445% on the route-weighted index since 1977.

+445%Since 1977TrendPercent 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 →
7Routes 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 →
34YearsYears 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 ConnecticutNotable 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 Connecticut: up 444% on the route-weighted index since 1977.

Marsh Wren Population Forecast in Connecticut

If the recent trend holds, Marsh Wren in Connecticut is projected to fall about 12% by 2029 — from 0.78 in 2024 to a central estimate of 0.68 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±69.5%, with 100% of held-out values landing inside the 95% band.

-12%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 →
0.68Projected 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 →
0.00–1.695% 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 →
±69.5%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 Connecticut is projected to fall about 12% by 2029 — from 0.78 in 2024 to a central estimate of 0.68 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±69.5%, with 100% of held-out values landing inside the 95% band.19732029
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 →
20250.670.001.6
20260.680.001.6
20270.680.001.6
20280.680.001.6
20290.680.001.6

Marsh Wren Survey Routes in Connecticut

Routes recording Marsh Wren in Connecticut.
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 →
Westbrook520241975
Warren 2220242024
Mystic120172017
Buckingham120142014
Woodstock119951986
Danbury119731973
Mid Haddam119801980

Marsh Wren Population Trend in Other States

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

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