BirdAnalyst
Guild · California · BBS 2026 Release · 1966–2025

Grassland Birds In California

All statesCalifornia

7 species in this guild. As a group they are -70%Guild trendA mean-index aggregate across the species in this group — the structural direction of the guild, with individual-species noise smoothed out.Full methodology → since 1970.

Guild SignalsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

guild collapsecomputed 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 →

Grassland birds as a group have fallen sharply in California, down 70% since 1970.

Grassland Birds In California Population Forecast

If the recent trend holds, Grassland birds in California is projected to fall about 49% by 2030 — from 3.6 in 2025 to a central estimate of 1.8 (95% range 0.00–4.0). A 5-year backtest shows a typical error of ±22.4%, with 100% of held-out values landing inside the 95% band.

-49%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 →
1.8Projected 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 →
0.00–4.095% 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 →
±22.4%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, Grassland birds in California is projected to fall about 49% by 2030 — from 3.6 in 2025 to a central estimate of 1.8 (95% range 0.00–4.0). A 5-year backtest shows a typical error of ±22.4%, 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 →
20262.30.034.5
20272.10.004.4
20282.00.004.3
20291.90.004.1
20301.80.004.0

Member Species In California

Grassland birds species in California.
TrendPercent 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 →
Loggerhead ShrikeLaniidae-86%
Horned LarkAlaudidae-74%
Western MeadowlarkIcteridae-51%
Lark SparrowPasserellidae-45%
Grasshopper SparrowPasserellidae+77%
Savannah SparrowPasserellidae+107%
Vesper SparrowPasserellidae+993%

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