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

Blue Grosbeak Population Trend in Pennsylvania

All statesGeneralists

Blue Grosbeak in Pennsylvania has collapsed: down 77% on the route-weighted index since 1976.

-77%Since 1976TrendPercent 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 →
38YearsYears 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 PennsylvaniaNotable 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 →

Blue Grosbeak has collapsed in Pennsylvania: down 77% on the route-weighted index since 1976.

Blue Grosbeak Population Forecast in Pennsylvania

If the recent trend holds, Blue Grosbeak in Pennsylvania is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.11). A 5-year backtest shows a typical error of ±58.4%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.01Projected 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 →
0.00–0.1195% 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 →
±58.4%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 Pennsylvania is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.11). A 5-year backtest shows a typical error of ±58.4%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20250.020.000.11
20260.020.000.11
20270.020.000.11
20280.010.000.11
20290.010.000.11

Blue Grosbeak Survey Routes in Pennsylvania

Routes recording Blue Grosbeak in Pennsylvania.
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 →
Scheafferstn1919761976
Shrewsbury420171991
Pottersdale219971997
Millville219761976
Needmore219911969
Landisburg120212013
Doylesburg120192019
Mount Joy119961990
Parkwood119921992
Mt Gretna 2120142014
Brunnerville 2120212021
Schaefferstown 2120222022
Schwenksvill119931989
Mill Run120092009
Waterstreet120132011
Stoneybreak120241993
Bendersville120141999
St College119861986
Jacobus120181986
Clear Spring120212021
Chatham120242003
Hometown120222004
Doe Run120141972
West Grove119781976

Blue Grosbeak Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamarylandminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomasouth-carolinasouth-dakotatennesseetexasutahvirginiawest-virginiawyoming

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