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Species · Arizona · BBS 2026 Release · 1966–2025

Grace's Warbler Population Trend in Arizona

All statesForest birds

Grace's Warbler in Arizona has surged: up 108% on the route-weighted index since 1970.

+108%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 →
23Routes 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 →
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 Grace's Warbler 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 →

Grace's Warbler has surged in Arizona: up 108% on the route-weighted index since 1970.

Grace's Warbler Population Forecast in Arizona

If the recent trend holds, Grace's Warbler in Arizona is projected to fall about 43% by 2030 — from 4.9 in 2025 to a central estimate of 2.8 (95% range 0.91–4.6). A 5-year backtest shows a typical error of ±13.9%, with 80% of held-out values landing inside the 95% band.

-43%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 →
2.8Projected 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 →
0.91–4.695% 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 →
±13.9%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, Grace's Warbler in Arizona is projected to fall about 43% by 2030 — from 4.9 in 2025 to a central estimate of 2.8 (95% range 0.91–4.6). A 5-year backtest shows a typical error of ±13.9%, with 80% 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 →
20262.70.874.6
20272.70.884.6
20282.80.894.6
20292.80.904.6
20302.80.914.6

Grace's Warbler Survey Routes in Arizona

Routes recording Grace's Warbler 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 →
Happy Jack7920251977
Tonto Vill.3820251992
Sawmill3720141988
Tsaile2820231993
Sprucedale1820251992
Aztec Peak1619781974
Rucker1120091993
Mt. Graham1120251995
Alpine1020251992
Prescott920251975
Dry Park920251992
Forest Lakes920251992
Flagstaff820221988
Portal620251975
Williams620252001
Carr Mtn520251985
Zeniff319681968
Blue319911974
Sunizona319751974
Maine220211997
Pinetop220221994
Round Rock119761969
Mormon Lake119751968

Grace's Warbler Population Trend in Other States

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