BirdAnalyst
Species · BCR 23 · BBS 2025 Release · 1966–2024

Double-crested Cormorant In Prairie Hardwood Transition

All regionsPrairie Hardwood TransitionWetland birds

Double-crested Cormorant in Prairie Hardwood Transition has surged: up 302% on the route-weighted index since 1975.

+302%Since 1975TrendPercent 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 →
59Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
50YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 Prairie Hardwood Transition: up 302% on the route-weighted index since 1975.

Forecast

If the recent trend holds, Double-crested Cormorant in Prairie Hardwood Transition is projected to rise about 88% by 2029 — from 0.55 in 2024 to a central estimate of 1.0 (95% range 0.14–1.9). A 5-year backtest shows a typical error of ±113%, with 100% of held-out values landing inside the 95% band.

+88%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 →
1.0Projected 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 →
0.14–1.995% 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 →
±113%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 Prairie Hardwood Transition is projected to rise about 88% by 2029 — from 0.55 in 2024 to a central estimate of 1.0 (95% range 0.14–1.9). A 5-year backtest shows a typical error of ±113%, 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 →
20250.980.091.9
20260.990.101.9
20271.00.121.9
20281.00.131.9
20291.00.141.9

Routes In Prairie Hardwood Transition

Routes recording Double-crested Cormorant in Prairie Hardwood Transition.
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 →
HudsonWISCONSIN462024
Rolling GrndWISCONSIN252009
N AndoverWISCONSIN212006
EdenWISCONSIN161998
EvergreenMINNESOTA132005
VickeryOHIO122015
Rolling PrWISCONSIN112022
Le CenterMINNESOTA72023
PrincetonMINNESOTA62013
GlenwoodMINNESOTA62019
ColbyWISCONSIN62003
CochraneWISCONSIN52009
ManawaWISCONSIN51995
St CharlesMICHIGAN42018
MillvilleMINNESOTA41997
HebronWISCONSIN42013
BeloitWISCONSIN42024
EdwardsMINNESOTA32023
New LondonMINNESOTA32012
Sherburne NrMINNESOTA32023
EsdaileWISCONSIN32001
MiddleburyINDIANA22015
LakevilleINDIANA22003
Big Blue LkMICHIGAN22024
OsseoMINNESOTA22017

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