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

Bell's Vireo Population Trend in Arizona

All statesForest birds

Bell's Vireo in Arizona has increased: up 35% on the route-weighted index since 1970.

+35%Since 1970TrendPercent 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 →
43Routes 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 →
56YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Bell's Vireo Trends in ArizonaNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Bell's Vireo in Arizona. See the full index history below.

Bell's Vireo Population Forecast in Arizona

If the recent trend holds, Bell's Vireo in Arizona is projected to stay roughly flat through 2029, near 4.0 (95% range 2.1–5.9). A 5-year backtest shows a typical error of ±36.6%, with 100% of held-out values landing inside the 95% band.

-3%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 →
4.0Projected 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 →
2.1–5.995% 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 →
±36.6%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, Bell's Vireo in Arizona is projected to stay roughly flat through 2029, near 4.0 (95% range 2.1–5.9). A 5-year backtest shows a typical error of ±36.6%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20253.91.95.8
20263.92.05.8
20273.92.05.9
20284.02.05.9
20294.02.15.9

Bell's Vireo Survey Routes in Arizona

Routes recording Bell's Vireo in Arizona.
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 →
Pomerene9120241968
Amado2220231993
Cutter 21720182015
Carr Mtn1720241985
Redington1420231993
Cutter1320141992
Pisinimo1019931992
Sunizona819971970
Bartlett Res720241993
Peña Blanca620241975
Patagonia620241969
Sahuarita420241992
Ajo320011968
Skull Valley320242001
Red Rock320141995
Peach Spring320242005
Casa Grande320231989
Ajo 2320172011
Florence219881971
San Simon220242023
Red Rock 2220242015
Mcneal220241992
Organ Pipe120211991
The Gap119731968
Dragoon120011993

Bell's Vireo Population Trend in Other States

arkansascaliforniacoloradoillinoisindianaiowakansaskentuckymichiganminnesotamissourinebraskanevadanew-mexiconorth-dakotaohiooklahomasouth-dakotatexasutahwisconsin

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