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Species · Louisiana · BBS 2025 Release · 1966–2024

Neotropic Cormorant Population Trend in Louisiana

All statesWetland birds

Neotropic Cormorant in Louisiana has collapsed: down 75% on the route-weighted index since 1973.

-75%Since 1973TrendPercent 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 →
24Routes 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 →
48YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Neotropic Cormorant Trends in LouisianaNotable 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 →

Neotropic Cormorant has collapsed in Louisiana: down 75% on the route-weighted index since 1973.

Neotropic Cormorant Population Forecast in Louisiana

If the recent trend holds, Neotropic Cormorant in Louisiana is projected to rise about 61% by 2029 — from 2.1 in 2024 to a central estimate of 3.4 (95% range 0.00–10). A 5-year backtest shows a typical error of ±71.7%, with 100% of held-out values landing inside the 95% band.

+61%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 →
3.4Projected 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 →
0.00–1095% 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 →
±71.7%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, Neotropic Cormorant in Louisiana is projected to rise about 61% by 2029 — from 2.1 in 2024 to a central estimate of 3.4 (95% range 0.00–10). A 5-year backtest shows a typical error of ±71.7%, with 100% of held-out values landing inside the 95% band.19702029
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 →
20253.30.0010
20263.30.0010
20273.30.0010
20283.30.0010
20293.40.0010

Neotropic Cormorant Survey Routes in Louisiana

Routes recording Neotropic Cormorant in Louisiana.
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 →
Forked Island 231120112010
Woodlawn4820212010
Sabine Nwr4220081989
Sabine Nwr 23720172009
Maurice3220241997
Creole1619801970
Ltl Chenier 21620112010
Richard1520242013
Esther1320241989
Gran Chenier1119821970
Forked Island1120242008
Ramah820242010
River Road720242016
Frogmore720232021
Kaplan620231998
Hackberry220161973
Vinton 2220192011
Atchafalaya120232013
Keystone120131995
Shaw120212021
Zwolle120172017
Berwick120102010
Ltl Chenier120232013
Hackberry 2120182018

Neotropic Cormorant Population Trend in Other States

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