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Species · Montana · BBS 2026 Release · 1966–2025

Double-crested Cormorant Population Trend in Montana

All statesWetland birds

Double-crested Cormorant in Montana has risen sharply: up 64% on the route-weighted index since 1979.

+64%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 →
42Routes 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 →
47YearsYears 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 risen sharply in Montana: up 64% 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 147% by 2030 — from 0.34 in 2025 to a central estimate of 0.83 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±46.6%, with 80% of held-out values landing inside the 95% band.

+147%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 →
0.83Projected 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 →
0.00–1.995% 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 →
±46.6%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 147% by 2030 — from 0.34 in 2025 to a central estimate of 0.83 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±46.6%, with 80% of held-out values landing inside the 95% band.19682030
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 →
20260.780.001.9
20270.800.001.9
20280.810.001.9
20290.820.001.9
20300.830.001.9

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 →
Chinook1820172015
Two Dot1520251991
Great Falls920161987
Augusta820221976
Roundup520192016
Harlem420011991
Powderville420252025
Hebgen Lake420232017
Malta320181980
Redstone320041990
Arlee319881988
Forsyth320042004
St Xavier319931993
Wheat Basin320242021
Willow Creek 2220251997
Savage219871987
Boulder220032003
Albion219931993
Beaverhead220241986
East Glacier Park220182018
Ester Lake220252016
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 2026-08-14.