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Species · Louisiana · BBS 2026 Release · 1966–2025

Blue Grosbeak Population Trend in Louisiana

All statesForest birds

Blue Grosbeak in Louisiana has surged: up 383% on the route-weighted index since 1969.

+383%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 →
84Routes 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 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 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 Louisiana: up 383% on the route-weighted index since 1969.

Blue Grosbeak Population Forecast in Louisiana

If the recent trend holds, Blue Grosbeak in Louisiana is projected to fall about 32% by 2030 — from 4.9 in 2025 to a central estimate of 3.3 (95% range 1.6–5.1). A 5-year backtest shows a typical error of ±18.2%, with 80% of held-out values landing inside the 95% band.

-32%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 →
3.3Projected 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 →
1.6–5.195% 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 →
±18.2%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 Louisiana is projected to fall about 32% by 2030 — from 4.9 in 2025 to a central estimate of 3.3 (95% range 1.6–5.1). A 5-year backtest shows a typical error of ±18.2%, with 80% 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 →
20263.21.54.9
20273.21.55.0
20283.31.55.0
20293.31.65.0
20303.31.65.1

Blue Grosbeak Survey Routes in Louisiana

Routes recording Blue Grosbeak 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 →
Transylvania2020251998
Trout1820251994
Mount Union1420251998
Fillmore1319891968
Many1219921989
Ivan1220131998
Ivan 21120252014
Flat Creek1020251998
Vinton 21020252011
Bickham920251984
Easton919901976
Frogmore920251998
Evelyn920242004
Shaw820231967
Cheniere820251984
Hargis820102006
Mayflower720251969
Derry719891970
Norwood720252006
Womack720251999
Linville720251998
Concord720192006
Enterprise720252006
Turkey Creek719981998
Derry 2620251990

Blue Grosbeak Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckymarylandminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvirginiawest-virginiawyoming

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