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

Cassin's Sparrow In Sierra Madre Occidental

All regionsSierra Madre OccidentalGrassland birds

Cassin's Sparrow in Sierra Madre Occidental has collapsed: down 79% on the route-weighted index since 1971.

-79%Since 1971TrendPercent 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 →
15Routes 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 →
37YearsYears 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 →

Cassin's Sparrow has collapsed in Sierra Madre Occidental: down 79% on the route-weighted index since 1971.

Forecast

If the recent trend holds, Cassin's Sparrow in Sierra Madre Occidental is projected to fall about 99% by 2029 — from 0.94 in 2024 to a central estimate of 0.01 (95% range 0.00–2.9). A 5-year backtest shows a typical error of ±124.1%, with 100% of held-out values landing inside the 95% band.

-99%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 →
0.01Projected 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 →
0.00–2.995% 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 →
±124.1%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, Cassin's Sparrow in Sierra Madre Occidental is projected to fall about 99% by 2029 — from 0.94 in 2024 to a central estimate of 0.01 (95% range 0.00–2.9). A 5-year backtest shows a typical error of ±124.1%, 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 →
20250.150.003.1
20260.120.003.0
20270.080.003.0
20280.050.003.0
20290.010.002.9

Routes In Sierra Madre Occidental

Routes recording Cassin's 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 →
Sunizona 2ARIZONA172024
McnealARIZONA152019
SunizonaARIZONA81992
MagdalenaNEW-MEXICO42017
San SimonARIZONA32019
Vicks PeakNEW-MEXICO31992
RuckerARIZONA21998
PomereneARIZONA12021
Peña BlancaARIZONA11993
PatagoniaARIZONA12001
AmadoARIZONA12022
SahuaritaARIZONA12023
Clay SpringARIZONA12011
Carr MtnARIZONA12008
DragoonARIZONA12007

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