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

Double-crested Cormorant Population Trend in Maine

All statesWetland birds

Double-crested Cormorant in Maine has increased: up 42% on the route-weighted index since 1971.

+42%Since 1971TrendPercent 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 →
34Routes 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 →
53YearsYears 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 MaineNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Double-crested Cormorant in Maine. See the full index history below.

Double-crested Cormorant Population Forecast in Maine

If the recent trend holds, Double-crested Cormorant in Maine is projected to fall about 31% by 2029 — from 0.63 in 2024 to a central estimate of 0.44 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±71.9%, with 100% of held-out values landing inside the 95% band.

-31%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 →
0.44Projected 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 →
0.00–1.495% 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 →
±71.9%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 Maine is projected to fall about 31% by 2029 — from 0.63 in 2024 to a central estimate of 0.44 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±71.9%, with 100% 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 →
20250.480.001.4
20260.470.001.4
20270.460.001.4
20280.450.001.4
20290.440.001.4

Double-crested Cormorant Survey Routes in Maine

Routes recording Double-crested Cormorant in Maine.
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 →
Deblois5820071968
Jefferson2120071996
Cornville1420232019
Eastbrook719961981
St David720052004
Cambridge519821982
Rome520052005
Hartford420001976
Hancock420241977
Medway420141976
Kittery Pt320241971
Freedom319751975
Harmony320241994
Hermon319831983
Castine320061976
Cape Neddick220241976
Greenwood220091994
Manchester219831977
Brooks219851983
Newcastle120081971
Wilson Mills120131992
Bethel119911991
Turner120021987
Reeds119971997
Otisfield Gr119991999

Double-crested Cormorant Population Trend in Other States

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

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