BirdAnalyst
Species · Tennessee · BBS 2025 Release · 1966–2024

Blue Grosbeak Population Trend in Tennessee

All statesGeneralists

Blue Grosbeak in Tennessee has surged: up 352% on the route-weighted index since 1968.

+352%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 →
53Routes 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 TennesseeNotable 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 Tennessee: up 352% on the route-weighted index since 1968.

Blue Grosbeak Population Forecast in Tennessee

If the recent trend holds, Blue Grosbeak in Tennessee is projected to fall about 23% by 2029 — from 8.6 in 2024 to a central estimate of 6.6 (95% range 5.3–8.0). A 5-year backtest shows a typical error of ±19.7%, with 60% of held-out values landing inside the 95% band.

-23%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 →
6.6Projected 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 →
5.3–8.095% 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 →
±19.7%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, Blue Grosbeak in Tennessee is projected to fall about 23% by 2029 — from 8.6 in 2024 to a central estimate of 6.6 (95% range 5.3–8.0). A 5-year backtest shows a typical error of ±19.7%, with 60% 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 →
20256.35.07.7
20266.45.07.8
20276.55.17.9
20286.65.27.9
20296.65.38.0

Blue Grosbeak Survey Routes in Tennessee

Routes recording Blue Grosbeak in Tennessee.
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 →
Mansfield3020241966
Glen2520241966
Tibbs1920241972
Brownsville1720241966
Big Sandy1620241967
Humboldt1420241966
Collinwood1320241966
Silerton1220241970
Campbellsville1220171966
Union Hill1120241968
Sweetlips820231966
Trenton820231973
Tiptonville720231969
Silver Pt720241969
Wrigley620221970
Bradyville520211968
Jefferson Cty520111966
Walland519891966
Mt Olive520191967
Cornpone520241990
Jones Gap520191982
Trace Lewis520172013
Whiteville420241966
Pond Creek420241971
Jasper420241969

Blue Grosbeak Population Trend in Other States

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