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

Vesper Sparrow Population Trend in Montana

All statesGrassland birds

Vesper Sparrow in Montana has risen sharply: up 70% on the route-weighted index since 1970.

+70%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 →
105Routes 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 Vesper Sparrow Trends in MontanaNotable 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 →

Vesper Sparrow has risen sharply in Montana: up 70% on the route-weighted index since 1970.

Vesper Sparrow Population Forecast in Montana

If the recent trend holds, Vesper Sparrow in Montana is projected to fall about 10% by 2029 — from 32 in 2024 to a central estimate of 28 (95% range 18–39). A 5-year backtest shows a typical error of ±8.9%, with 100% of held-out values landing inside the 95% band.

-10%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 →
28Projected 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 →
18–3995% 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 →
±8.9%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, Vesper Sparrow in Montana is projected to fall about 10% by 2029 — from 32 in 2024 to a central estimate of 28 (95% range 18–39). A 5-year backtest shows a typical error of ±8.9%, 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 →
2025281838
2026281838
2027281838
2028281839
2029281839

Vesper Sparrow Survey Routes in Montana

Routes recording Vesper Sparrow in Montana.
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 →
Redstone18420241975
Whitlash13220242009
Polson13120241972
Beaverhead10120241973
Boulder10020241969
Custer9920222019
Wolf Creek8820222015
Custer 28720242024
Augusta8620241976
Shawmut8520241979
Freeman Creek8120162015
Fort Logan8020242018
Hay Lake7420221988
Westby7120242015
Heart Butte7020242015
Brusett6620241982
Winnett6620232017
Sunburst6220071970
St. Mary 26020242009
St Mary5720081972
Brunzell Slough5720242015
Leroy5620241970
Two Dot5520241976
Roundup5520242016
Cleveland5420241979

Vesper Sparrow Population Trend in Other States

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

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