BirdAnalyst
Species · South Dakota · BBS 2026 Release · 1966–2025

Blue Grosbeak Population Trend in South Dakota

All statesForest birds

Blue Grosbeak in South Dakota has surged: up 284% on the route-weighted index since 1969.

+284%Since 1969TrendPercent 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 →
35Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Blue Grosbeak Trends in South DakotaNotable 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 →

Blue Grosbeak has surged in South Dakota: up 284% on the route-weighted index since 1969.

Blue Grosbeak Population Forecast in South Dakota

If the recent trend holds, Blue Grosbeak in South Dakota is projected to fall about 80% by 2030 — from 2.9 in 2025 to a central estimate of 0.58 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±77%, with 20% of held-out values landing inside the 95% band.

-80%Change by 2030TrendPercent 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 →
0.58Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.595% 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 →
±77%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, Blue Grosbeak in South Dakota is projected to fall about 80% by 2030 — from 2.9 in 2025 to a central estimate of 0.58 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±77%, with 20% of held-out values landing inside the 95% band.19672030
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 →
20260.580.001.5
20270.580.001.5
20280.580.001.5
20290.580.001.5
20300.580.001.5

Blue Grosbeak Survey Routes in South Dakota

Routes recording Blue Grosbeak in South Dakota.
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 →
Badlands2420251982
Cedar Pass1520251969
Rockyford1120251970
Tripp820251968
Howard620251972
White River620141995
Railroad Butte420222018
Eagle Butte420111990
Winner320251970
Rosebud320111967
Volunteer320251967
Lacreek320252013
Lennox220251969
Cottonwood219961996
Owanka219751973
Fort Pierre220231969
Lodgepole220252025
White Lake119781978
Geddes120251967
Chamberlain120111970
Volga120251981
Raymond120122012
Roswell119951970
Lane119701970
Ft Thompson120111968

Blue Grosbeak Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamarylandminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniasouth-carolinatennesseetexasutahvirginiawest-virginiawyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.