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

Wetland Birds In California

All statesCalifornia

33 species in this guild. As a group they are +22%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 →

No notable trend signals for wetland birds in California. See the full index history below.

Wetland Birds In California Population Forecast

If the recent trend holds, Wetland birds in California is projected to rise about 117% by 2029 — from 0.71 in 2024 to a central estimate of 1.5 (95% range 0.51–2.6). A 5-year backtest shows a typical error of ±198.5%, with 20% of held-out values landing inside the 95% band.

+117%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 →
1.5Projected 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 →
0.51–2.695% 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 →
±198.5%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, Wetland birds in California is projected to rise about 117% by 2029 — from 0.71 in 2024 to a central estimate of 1.5 (95% range 0.51–2.6). A 5-year backtest shows a typical error of ±198.5%, with 20% 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 →
20251.50.472.5
20261.50.482.5
20271.50.492.5
20281.50.502.5
20291.50.512.6

Member Species In California

Wetland 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 →
Heermann's GullLaridae-95%
Western GullLaridae-84%
Common GallinuleRallidae-82%
Western GrebePodicipedidae-80%
Black TernLaridae-77%
Pelagic CormorantPhalacrocoracidae-74%
Forster's TernLaridae-60%
Clark's GrebePodicipedidae-34%
American BitternArdeidae-34%
Caspian TernLaridae-33%
Ridgway's RailRallidae-30%
Glaucous-winged GullLaridae-26%
Green HeronArdeidae-10%
Pied-billed GrebePodicipedidae+3%
Ring-billed GullLaridae+8%
Great Blue HeronArdeidae+19%
American CootRallidae+23%
California GullLaridae+26%
Least TernLaridae+26%
Franklin's GullLaridae+45%
Sandhill CraneGruidae+51%
Virginia RailRallidae+64%
Double-crested CormorantPhalacrocoracidae+69%
Eared GrebePodicipedidae+83%
SoraRallidae+94%
Snowy EgretArdeidae+95%
Brandt's CormorantPhalacrocoracidae+109%
Western Cattle-EgretArdeidae+116%
Black-crowned Night HeronArdeidae+152%
American White PelicanPelecanidae+213%
Brown PelicanPelecanidae+525%
White-faced IbisThreskiornithidae24×
Great EgretArdeidae43×

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