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

Marsh Wren Population Trend in Colorado

All statesForest birds

Marsh Wren in Colorado has fallen sharply: down 66% on the route-weighted index since 1992.

-66%Since 1992TrendPercent 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 →
31YearsYears 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 ColoradoNotable 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 →

Marsh Wren has fallen sharply in Colorado: down 66% on the route-weighted index since 1992.

Marsh Wren Population Forecast in Colorado

If the recent trend holds, Marsh Wren in Colorado is projected to fall about 100% by 2029 — from 0.06 in 2024 to a central estimate of 0.00 (95% range 0.00–0.21). A 5-year backtest shows a typical error of ±204.9%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–0.2195% 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 →
±204.9%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 Colorado is projected to fall about 100% by 2029 — from 0.06 in 2024 to a central estimate of 0.00 (95% range 0.00–0.21). A 5-year backtest shows a typical error of ±204.9%, with 100% of held-out values landing inside the 95% band.19892029
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 →
20250.000.000.21
20260.000.000.21
20270.000.000.21
20280.000.000.21
20290.000.000.21

Marsh Wren Survey Routes in Colorado

Routes recording Marsh Wren in Colorado.
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 →
Arsenal520021991
Yellowjacket Pass320182018
Maybell320241992
Walden320242010
Moffat319951993
Alamosa320171989
Paonia320032003
San Luis320001991
Hudson220151994
Browns Park220211995
Lay220122009
Marshall Pas220121998
Dinosaur120122012
Doyleville120222022
Cortez120071997
Angora120222022

Marsh Wren Population Trend in Other States

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

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