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

Double-crested Cormorant Population Trend in Michigan

All statesWetland birds

Double-crested Cormorant in Michigan has fallen sharply: down 69% on the route-weighted index since 1991.

-69%Since 1991TrendPercent 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 →
15Routes 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 →
22YearsYears 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 MichiganNotable 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 →

Double-crested Cormorant has fallen sharply in Michigan: down 69% on the route-weighted index since 1991.

Double-crested Cormorant Population Forecast in Michigan

If the recent trend holds, Double-crested Cormorant in Michigan is projected to fall about 92% by 2029 — from 0.06 in 2024 to a central estimate of 0.01 (95% range 0.00–0.30). A 5-year backtest shows a typical error of ±183.9%, with 100% of held-out values landing inside the 95% band.

-92%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 →
0.01Projected 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 →
0.00–0.3095% 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 →
±183.9%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, Double-crested Cormorant in Michigan is projected to fall about 92% by 2029 — from 0.06 in 2024 to a central estimate of 0.01 (95% range 0.00–0.30). A 5-year backtest shows a typical error of ±183.9%, with 100% of held-out values landing inside the 95% band.19882029
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 →
20250.020.000.32
20260.020.000.31
20270.010.000.31
20280.010.000.30
20290.010.000.30

Double-crested Cormorant Survey Routes in Michigan

Routes recording Double-crested Cormorant in Michigan.
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 →
Isabella519881988
St Charles420181991
Bootjack319981992
Maple Grove219921992
Ishpeming219911990
Big Blue Lk220242013
Cathro219951995
Galesburg120102010
Hungerford120122012
Herman119931991
Deckerville120042004
Pickford120002000
Richmond120242024
Muskallonge119971997
Prattville120022002

Double-crested Cormorant Population Trend in Other States

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

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