BirdAnalyst
Guild · California · BBS 2025 Release · 1966–2024

Grassland Birds In California

All statesCalifornia

7 species in this guild. As a group they are -72%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 72% since 1970.

Grassland Birds In California Population Forecast

If the recent trend holds, Grassland birds in California is projected to fall about 44% by 2029 — from 3.3 in 2024 to a central estimate of 1.9 (95% range 0.00–3.8). A 5-year backtest shows a typical error of ±14.3%, with 100% of held-out values landing inside the 95% band.

-44%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 →
1.9Projected 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 →
0.00–3.895% 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 →
±14.3%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 44% by 2029 — from 3.3 in 2024 to a central estimate of 1.9 (95% range 0.00–3.8). A 5-year backtest shows a typical error of ±14.3%, 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 →
20252.30.394.2
20262.20.284.1
20272.10.164.0
20282.00.053.9
20291.90.003.8

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 →
Ring-necked PheasantPhasianidae-91%
Horned LarkAlaudidae-74%
Western MeadowlarkIcteridae-57%
Lark SparrowPasserellidae-50%
Savannah SparrowPasserellidae+65%
Grasshopper SparrowPasserellidae+197%
Vesper SparrowPasserellidae+638%

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