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

Vesper Sparrow Population Trend in Arizona

All statesGrassland birds

Vesper Sparrow in Arizona has declined: down 43% on the route-weighted index since 1970.

-43%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 →
25Routes 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 →
50YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Vesper Sparrow 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 Vesper Sparrow in Arizona. See the full index history below.

Vesper Sparrow Population Forecast in Arizona

If the recent trend holds, Vesper Sparrow in Arizona is projected to fall about 21% by 2029 — from 0.43 in 2024 to a central estimate of 0.34 (95% range 0.00–2.3). A 5-year backtest shows a typical error of ±50.8%, with 100% of held-out values landing inside the 95% band.

-21%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 →
0.34Projected 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 →
0.00–2.395% 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 →
±50.8%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, Vesper Sparrow in Arizona is projected to fall about 21% by 2029 — from 0.43 in 2024 to a central estimate of 0.34 (95% range 0.00–2.3). A 5-year backtest shows a typical error of ±50.8%, 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 →
20250.420.002.4
20260.400.002.3
20270.380.002.3
20280.360.002.3
20290.340.002.3

Vesper Sparrow Survey Routes in Arizona

Routes recording Vesper Sparrow 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 →
Alpine1520231992
Black Mesa1419951989
Rose Wells1419781968
Yampai1219771975
Maine1220241992
Pinetop1120221993
Flagstaff920221988
House Rock519931976
Mormon Lake519751968
Clay Spring520211988
Round Rock419891969
Cow Springs420002000
Williams420192006
Navajo Trail420112011
Sprucedale420232003
Sawmill320101988
Castle Butte319941992
Happy Jack320241991
Tsaile220181993
Oraibi120181994
Hunt120061976
Blue119851976
Greasewood119951995
Forest Lakes120221994
Kaibito120101993

Vesper Sparrow Population Trend in Other States

californiacoloradoconnecticutdelawareidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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