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Species · Montana · BBS 2025 Release · 1966–2024

Double-crested Cormorant Population Trend in Montana

All statesWetland birds

Double-crested Cormorant in Montana has surged: up 400% on the route-weighted index since 1979.

+400%Since 1979TrendPercent 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 →
40Routes 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 →
46YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Double-crested Cormorant Trends in MontanaNotable 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 →

Double-crested Cormorant has surged in Montana: up 400% on the route-weighted index since 1979.

Double-crested Cormorant Population Forecast in Montana

If the recent trend holds, Double-crested Cormorant in Montana is projected to rise about 27% by 2029 — from 0.68 in 2024 to a central estimate of 0.87 (95% range 0.00–2.0). A 5-year backtest shows a typical error of ±36.1%, with 80% of held-out values landing inside the 95% band.

+27%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 →
0.87Projected 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 →
0.00–2.095% 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 →
±36.1%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, Double-crested Cormorant in Montana is projected to rise about 27% by 2029 — from 0.68 in 2024 to a central estimate of 0.87 (95% range 0.00–2.0). A 5-year backtest shows a typical error of ±36.1%, with 80% of held-out values landing inside the 95% band.19682029
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 →
20250.810.001.9
20260.820.001.9
20270.840.001.9
20280.850.001.9
20290.870.002.0

Double-crested Cormorant Survey Routes in Montana

Routes recording Double-crested Cormorant in Montana.
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 →
Two Dot5020241991
Chinook1820172015
Glasgow1719681968
Great Falls920161987
Augusta820221976
Roundup520192016
Harlem420011991
Hebgen Lake420232017
Malta320181980
Redstone320041990
Arlee319881988
Forsyth320042004
St Xavier319931993
Red Rock320231994
Ester Lake320212016
Wheat Basin320242021
Savage219871987
Boulder220032003
Albion219931993
Beaverhead220241986
East Glacier Park220182018
Kalispell120241995
Flatwillow 2120212013
Virgelle120241979
Cleveland119961982

Double-crested Cormorant Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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