BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Blue Grosbeak In Coastal California

All regionsCoastal CaliforniaGeneralists

Blue Grosbeak in Coastal California has risen sharply: up 63% on the route-weighted index since 1971.

+63%Since 1971TrendPercent 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 RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 risen sharply in Coastal California: up 63% on the route-weighted index since 1971.

Forecast

If the recent trend holds, Blue Grosbeak in Coastal California is projected to stay roughly flat through 2029, near 0.94 (95% range 0.10–1.8). A 5-year backtest shows a typical error of ±295.3%, with 60% of held-out values landing inside the 95% band.

+5%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 →
0.94Projected 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 →
0.10–1.895% 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 →
±295.3%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 Coastal California is projected to stay roughly flat through 2029, near 0.94 (95% range 0.10–1.8). A 5-year backtest shows a typical error of ±295.3%, with 60% 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 →
20250.890.051.7
20260.900.061.7
20270.910.071.8
20280.930.081.8
20290.940.101.8

Routes In Coastal California

Routes recording Blue Grosbeak in Coastal California.
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 →
Cp. PendletonCALIFORNIA292004
AtwaterCALIFORNIA102012
Jofegan 2CALIFORNIA92024
Staten Is.CALIFORNIA82024
AnzaCALIFORNIA72004
Tres Pinos 2CALIFORNIA72011
Elsinore MtnCALIFORNIA52024
Anza 2CALIFORNIA52024
MorenoCALIFORNIA42024
OrlandCALIFORNIA42015
AthloneCALIFORNIA42007
BakersfieldCALIFORNIA32003
Oak GroveCALIFORNIA32024
Mesa GrandeCALIFORNIA32024
Buena VistaCALIFORNIA31994
PenningtonCALIFORNIA22019
San YsidroCALIFORNIA22013
CopperopolisCALIFORNIA22024
OnealsCALIFORNIA22011
GreenfieldCALIFORNIA22024
CollegevilleCALIFORNIA11987
HughsonCALIFORNIA12019
CaruthersCALIFORNIA11982
Tres PinosCALIFORNIA12003
Santa YnezCALIFORNIA12019

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