BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Double-crested Cormorant

PhalacrocoracidaeWetland birdsNannopterum auritum

Double-crested Cormorant has surged: up 177% on the route-weighted index since 1968.

+177%Since 1968TrendPercent 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 →
1,213RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Double-crested Cormorant

The Double-crested Cormorant (Nannopterum auritum) is a North American member of the Cormorants (Phalacrocoracidae). In this analysis it is grouped with the wetland birds.

Size
27.5–35.5 in long (70–90 cm) — a large diving waterbird (typical for the family)
Habitat
Marshes, ponds, lakeshores and other freshwater wetlands.
Diet
Aquatic invertebrates, small fish, frogs and plant matter.
Range
Recorded on 1,213 Breeding Bird Survey routes across 49 states, most concentrated in the Southeastern Coastal Plain.
Family
Phalacrocoracidae · Wetland birds

Notable Double-crested Cormorant TrendsNotable 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 surveyed states: up 177% on the route-weighted index since 1968.

Double-crested Cormorant Population Forecast

If the recent trend holds, Double-crested Cormorant is projected to rise about 81% by 2029 — from 0.43 in 2024 to a central estimate of 0.78 (95% range 0.48–1.1). A 5-year backtest shows a typical error of ±82.3%, with 0% of held-out values landing inside the 95% band.

+81%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 →
0.78Projected 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 →
0.48–1.195% 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 →
±82.3%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 is projected to rise about 81% by 2029 — from 0.43 in 2024 to a central estimate of 0.78 (95% range 0.48–1.1). A 5-year backtest shows a typical error of ±82.3%, with 0% of held-out values landing inside the 95% band.19662029
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 →
20250.740.451.0
20260.750.461.0
20270.760.461.1
20280.770.471.1
20290.780.481.1

Where the Double-crested Cormorant Is Detected

BBS routes recording Double-crested Cormorant, sized by most recent count.

Double-crested Cormorant Population Trend by State

Double-crested Cormorant population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alabama38×198331
Alaskainsufficient datan/a4
Arizona-7%199115
Arkansas+6%19996
California+69%197473
Colorado19×198928
Connecticut-55%198112
Delaware+80%197513
Florida-94%196892
Georgia-28%198430
Idaho-76%198117
Illinois+721%198448
Indiana-67%201110
Iowa-75%199211
Kansas+834%197717
Kentuckyinsufficient datan/a8
Louisiana-32%197527
Maine+42%197134
Maryland+683%198140
Massachusetts+100%197123
Michigan-69%199115
Minnesota+241%197554
Mississippi13×200810
Missouri+11%200411
Montana+400%197940
Nebraska-49%198024
Nevada-80%19789
New Hampshire-6%198212
New Jersey+145%198124
New Mexico-10%19945
New York+267%198725
North Carolina+147%197940
North Dakota+686%197042
Ohio+59%199711
Oklahoma+720%199012
Oregon-72%197123
Pennsylvania-1%199131
Rhode Island+179%19855
South Carolina+50%199511
South Dakota+8%196933
Tennessee+431%199719
Texas+695%197557
Utah-81%198515
Vermont-42%19915
Virginia-21%198520
Washington-7%197638
West Virginiainsufficient datan/a4
Wisconsin+77%197841
Wyoming+14%197838

Double-crested Cormorant Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Double-crested Cormorant population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Northern Pacific Rainforest+19%197138
Great Basin+7%197175
Northern Rockies-5%198344
Prairie Potholes+235%196986
Boreal Hardwood Transition-78%198233
Lower Great Lakes / St. Lawrence Plain+216%199022
Atlantic Northern Forest+93%197150
Southern Rockies / Colorado Plateau13×197825
Badlands and Prairies12×196954
Shortgrass Prairie+308%198722
Central Mixed Grass Prairie+981%197432
Oaks and Prairies-52%198222
Eastern Tallgrass Prairie+859%198279
Prairie Hardwood Transition+302%197559
Central Hardwoods45×199627
West Gulf Coastal Plain / Ouachitas-47%198118
Mississippi Alluvial Valley+981%199327
Southeastern Coastal Plain16×1969113
Appalachian Mountains14×198863
Piedmont-0%198740
New England / Mid-Atlantic Coast25×1970111
Peninsular Florida-95%196870
Coastal California+599%197440
Sonoran and Mojave Deserts-34%197916
Sierra Madre Occidental-43%19935
Chihuahuan Desert+106%19966
Gulf Coastal Prairie+101%197526

Double-crested Cormorant Conservation Status

Our route-weighted index shows it up about 177% since 1968.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.