BirdAnalyst
Species · BCR 34 · BBS 2025 Release · 1966–2024

Black-chinned Sparrow In Sierra Madre Occidental

All regionsSierra Madre OccidentalGeneralists

Black-chinned Sparrow in Sierra Madre Occidental has fallen sharply: down 64% on the route-weighted index since 1976.

-64%Since 1976TrendPercent 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 →
16Routes 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 →
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 SignalsNotable 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 declinecomputed 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 →

Black-chinned Sparrow has fallen sharply in Sierra Madre Occidental: down 64% on the route-weighted index since 1976.

Forecast

If the recent trend holds, Black-chinned Sparrow in Sierra Madre Occidental is projected to rise about 20% by 2029 — from 0.72 in 2024 to a central estimate of 0.87 (95% range 0.00–2.0). A 5-year backtest shows a typical error of ±188.5%, with 100% of held-out values landing inside the 95% band.

+20%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 →
0.87Projected 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 →
0.00–2.095% 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 →
±188.5%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, Black-chinned Sparrow in Sierra Madre Occidental is projected to rise about 20% by 2029 — from 0.72 in 2024 to a central estimate of 0.87 (95% range 0.00–2.0). A 5-year backtest shows a typical error of ±188.5%, with 100% of held-out values landing inside the 95% band.19742029
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 →
20250.900.002.0
20260.900.002.0
20270.890.002.0
20280.880.002.0
20290.870.002.0

Routes In Sierra Madre Occidental

Routes recording Black-chinned 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 →
Aztec PeakARIZONA171978
CutterARIZONA72014
Emory PassNEW-MEXICO42024
Carr MtnARIZONA32024
Skull ValleyARIZONA22024
RuckerARIZONA21999
Vicks PeakNEW-MEXICO22024
PrescottARIZONA12022
PatagoniaARIZONA11987
Tonto Vill.ARIZONA12021
Bartlett ResARIZONA12024
SahuaritaARIZONA12019
PortalARIZONA12024
DragoonARIZONA11995
ReserveNEW-MEXICO12001
MagdalenaNEW-MEXICO12018

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