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

Grace's Warbler Population Trend in Arizona

All statesForest birds

Grace's Warbler in Arizona has risen sharply: up 65% on the route-weighted index since 1970.

+65%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 →
54YearsYears 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 risen sharply in Arizona: up 65% 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 stay roughly flat through 2029, near 2.6 (95% range 0.80–4.4). A 5-year backtest shows a typical error of ±6%, with 100% of held-out values landing inside the 95% band.

+1%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 →
2.6Projected 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 →
0.80–4.495% 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 →
±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, Grace's Warbler in Arizona is projected to stay roughly flat through 2029, near 2.6 (95% range 0.80–4.4). A 5-year backtest shows a typical error of ±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 →
20252.60.784.3
20262.60.784.3
20272.60.794.3
20282.60.794.4
20292.60.804.4

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 Jack6220241977
Sawmill3720141988
Tsaile2820231993
Tonto Vill.2320211992
Sprucedale2120231992
Aztec Peak1619781974
Mt. Graham1420231995
Rucker1120091993
Alpine1020231992
Forest Lakes920241992
Flagstaff820221988
Prescott720221975
Dry Park720241992
Carr Mtn620241985
Portal520241975
Zeniff319681968
Blue319911974
Sunizona319751974
Williams320182001
Maine220211997
Pinetop220221994
Round Rock119761969
Mormon Lake119751968

Grace's Warbler Population Trend in Other States

coloradonew-mexicoutah

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