BirdAnalyst
Species · BCR 34 · BBS 2026 Release · 1966–2025

Vesper Sparrow In Sierra Madre Occidental

All regionsSierra Madre OccidentalGrassland birds

Vesper Sparrow in Sierra Madre Occidental has declined: down 35% on the route-weighted index since 1970.

-35%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 →
11Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
45YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 Sierra Madre Occidental. See the full index history below.

Vesper Sparrow In Sierra Madre Occidental Population Forecast

If the recent trend holds, Vesper Sparrow in Sierra Madre Occidental is projected to fall about 47% by 2030 — from 2.6 in 2025 to a central estimate of 1.4 (95% range 0.00–3.5). A 5-year backtest shows a typical error of ±34.9%, with 100% of held-out values landing inside the 95% band.

-47%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 →
1.4Projected 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 →
0.00–3.595% 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 →
±34.9%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 Sierra Madre Occidental is projected to fall about 47% by 2030 — from 2.6 in 2025 to a central estimate of 1.4 (95% range 0.00–3.5). A 5-year backtest shows a typical error of ±34.9%, 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 →
20261.40.003.5
20271.40.003.5
20281.40.003.5
20291.40.003.5
20301.40.003.5

Routes In Sierra Madre Occidental

Routes recording Vesper Sparrow in Sierra Madre Occidental.
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 →
AlpineARIZONA292025
FlagstaffARIZONA162025
MaineARIZONA142025
PinetopARIZONA112022
Mormon LakeARIZONA51975
Clay SpringARIZONA52021
WilliamsARIZONA32025
Happy JackARIZONA32025
SprucedaleARIZONA32025
BlueARIZONA11985
Forest LakesARIZONA12025

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