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

Wetland Birds In California

All statesCalifornia

39 species in this guild. As a group they are -42%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 →

Wetland birds as a group have declined in California, down 42% since 1970.

Wetland Birds In California Population Forecast

If the recent trend holds, Wetland birds in California is projected to stay roughly flat through 2030, near 2.3 (95% range 0.44–4.2). A 5-year backtest shows a typical error of ±27.2%, with 100% of held-out values landing inside the 95% band.

-7%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 →
2.3Projected 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 →
0.44–4.295% 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 →
±27.2%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, Wetland birds in California is projected to stay roughly flat through 2030, near 2.3 (95% range 0.44–4.2). A 5-year backtest shows a typical error of ±27.2%, 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 →
20262.50.604.4
20272.50.564.3
20282.40.524.3
20292.40.484.3
20302.30.444.2

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-83%
Common GallinuleRallidae-82%
Western GrebePodicipedidae-78%
Black TernLaridae-77%
Pelagic CormorantPhalacrocoracidae-74%
Forster's TernLaridae-67%
Tricolored BlackbirdIcteridae-64%
Yellow-headed BlackbirdIcteridae-47%
Ridgway's RailRallidae-30%
Glaucous-winged GullLaridae-26%
Caspian TernLaridae-24%
American DipperCinclidae-23%
Clark's GrebePodicipedidae-22%
Belted KingfisherAlcedinidae-11%
Pied-billed GrebePodicipedidae-3%
Red-winged BlackbirdIcteridae+11%
American CootRallidae+16%
Green HeronArdeidae+16%
American BitternArdeidae+18%
California GullLaridae+19%
Least TernLaridae+26%
Eared GrebePodicipedidae+29%
Ring-billed GullLaridae+43%
Franklin's GullLaridae+45%
Great Blue HeronArdeidae+49%
SoraRallidae+50%
Double-crested CormorantPhalacrocoracidae+67%
Virginia RailRallidae+69%
Snowy EgretArdeidae+71%
Brandt's CormorantPhalacrocoracidae+87%
Western Cattle-EgretArdeidae+117%
Brown PelicanPelecanidae+145%
Sandhill CraneGruidae+167%
American White PelicanPelecanidae+178%
Black-crowned Night HeronArdeidae+209%
White-faced IbisThreskiornithidae31×
Great EgretArdeidae40×
Great-tailed GrackleIcteridae53×

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