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

Marsh Wren Population Trend in California

All statesForest birds

Marsh Wren in California has surged: up 958% on the route-weighted index since 1972.

+958%Since 1972TrendPercent 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 →
49Routes 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 Marsh Wren Trends in CaliforniaNotable 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 California: up 958% on the route-weighted index since 1972.

Marsh Wren Population Forecast in California

If the recent trend holds, Marsh Wren in California is projected to stay roughly flat through 2030, near 1.1 (95% range 0.46–1.7). A 5-year backtest shows a typical error of ±69.8%, with 80% of held-out values landing inside the 95% band.

+6%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 →
1.1Projected 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 →
0.46–1.795% 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 →
±69.8%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 California is projected to stay roughly flat through 2030, near 1.1 (95% range 0.46–1.7). A 5-year backtest shows a typical error of ±69.8%, with 80% of held-out values landing inside the 95% band.19702030
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 →
20261.10.431.7
20271.10.441.7
20281.10.451.7
20291.10.461.7
20301.10.461.7

Marsh Wren Survey Routes in California

Routes recording Marsh Wren in California.
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 →
Dorris7620191972
Staten Is.3620251994
Ora Loma1620251973
Glenn1320251972
Likely1120251974
Honey Lake620251977
Redwood N.P.520101995
Shafter519891987
Imperial Dam520101977
Redwood N.P. 2420132012
Bodega Bay420211972
Iron Gate319921992
Jofegan 2320252025
Tranquillity320041975
Cp. Pendleton320031972
Nubieber220181970
Crescent Cty220241972
Arvin219881982
Atwater220121973
Madeline220242010
Westley220141995
Macdoel220191992
Zamora220031987
Coyote219841984
Poway219801980

Marsh Wren Population Trend in Other States

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

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