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Species · Arizona · BBS 2026 Release · 1966–2025

Bell's Vireo Population Trend in Arizona

All statesForest birds

Bell's Vireo in Arizona has risen sharply: up 50% on the route-weighted index since 1970.

+50%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 →
57YearsYears 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 →

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 →

Bell's Vireo has risen sharply in Arizona: up 50% on the route-weighted index since 1970.

Bell's Vireo Population Forecast in Arizona

If the recent trend holds, Bell's Vireo in Arizona is projected to rise about 19% by 2030 — from 3.4 in 2025 to a central estimate of 4.0 (95% range 2.1–5.9). A 5-year backtest shows a typical error of ±35.6%, with 100% of held-out values landing inside the 95% band.

+19%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 →
4.0Projected 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 →
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 →
±35.6%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 rise about 19% by 2030 — from 3.4 in 2025 to a central estimate of 4.0 (95% range 2.1–5.9). A 5-year backtest shows a typical error of ±35.6%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20263.91.95.8
20273.92.05.8
20283.92.05.8
20294.02.05.9
20304.02.15.9

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 →
Pomerene6620251968
Cutter 21720182015
Redington1520251993
Cutter1320141992
Amado1320251993
Carr Mtn1120251985
Peña Blanca1020251975
Pisinimo1019931992
Sunizona819971970
Bartlett Res720251993
Patagonia620251969
Sahuarita420251992
Ajo320011968
Skull Valley320242001
Red Rock320141995
Peach Spring320242005
Casa Grande320231989
Ajo 2320172011
Florence219881971
San Simon220242023
Palo Verde 2220252017
Red Rock 2220242015
Mcneal220251992
Sunizona 2220252008
Organ Pipe120211991

Bell's Vireo Population Trend in Other States

arkansascaliforniacoloradoillinoisindianaiowakansaskentuckymichiganminnesotamissourinebraskanevadanew-mexiconorth-dakotaohiooklahomasouth-dakotatexasutahwisconsin

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