BirdAnalyst
Species · Delaware · BBS 2026 Release · 1966–2025

Blue Grosbeak Population Trend in Delaware

All statesForest birds

Blue Grosbeak in Delaware has surged: up 579% on the route-weighted index since 1968.

+579%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 →
17Routes 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 →
59YearsYears 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 DelawareNotable 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 Delaware: up 579% on the route-weighted index since 1968.

Blue Grosbeak Population Forecast in Delaware

If the recent trend holds, Blue Grosbeak in Delaware is projected to stay roughly flat through 2030, near 23 (95% range 15–30). A 5-year backtest shows a typical error of ±20.3%, with 100% of held-out values landing inside the 95% band.

-7%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 →
23Projected 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 →
15–3095% 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 →
±20.3%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 Delaware is projected to stay roughly flat through 2030, near 23 (95% range 15–30). A 5-year backtest shows a typical error of ±20.3%, with 100% of held-out values landing inside the 95% band.19662030
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 →
2026221429
2027221429
2028221530
2029221530
2030231530

Blue Grosbeak Survey Routes in Delaware

Routes recording Blue Grosbeak in Delaware.
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 →
Holleyville3720041966
Pepperbox 23520252017
Holleyville 23420242006
Millsboro3220252017
Blackbird2720251994
Pepperbox2620161998
Georgetown2520221992
Milton 22420252017
Harrington2220251969
Frankford1720121966
Milton1720161966
Frederica720251966
Lowes Xrds619911966
Dover419871966
Mt Pleasant220191966
Wilmington220131966
Bethany Bch219891967

Blue Grosbeak Population Trend in Other States

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

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