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

Grassland Birds In Colorado

All statesColorado

15 species in this guild. As a group they are -66%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 Colorado, down 66% since 1970.

Grassland Birds In Colorado Population Forecast

If the recent trend holds, Grassland birds in Colorado is projected to fall about 55% by 2030 — from 10 in 2025 to a central estimate of 4.5 (95% range 0.00–13). A 5-year backtest shows a typical error of ±36.2%, with 100% of held-out values landing inside the 95% band.

-55%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 →
4.5Projected 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 →
0.00–1395% 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 →
±36.2%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 Colorado is projected to fall about 55% by 2030 — from 10 in 2025 to a central estimate of 4.5 (95% range 0.00–13). A 5-year backtest shows a typical error of ±36.2%, 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 →
20266.20.0015
20275.70.0015
20285.30.0014
20294.90.0014
20304.50.0013

Member Species In Colorado

Grassland birds species in Colorado.
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 →
Chestnut-collared LongspurCalcariidae-96%
Upland SandpiperScolopacidae-94%
BobolinkIcteridae-89%
Lark BuntingPasserellidae-80%
Loggerhead ShrikeLaniidae-73%
Grasshopper SparrowPasserellidae-58%
Horned LarkAlaudidae-51%
Western MeadowlarkIcteridae-48%
Savannah SparrowPasserellidae+37%
Thick-billed LongspurCalcariidae+41%
Lark SparrowPasserellidae+177%
American PipitMotacillidae+221%
Cassin's SparrowPasserellidae+263%
DickcisselCardinalidae+896%
Vesper SparrowPasserellidae17×

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