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

Seabirds In California

All statesCalifornia

3 species in this guild. As a group they are -94%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 1974.

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 →

Seabirds as a group have collapsed in California, down 94% since 1974.

Forecast

If the recent trend holds, Seabirds in California is projected to stay roughly flat through 2027, near 0.00 (95% range 0.00–0.72). A 5-year backtest shows a typical error of ±674.9%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2027TrendPercent 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 →
0.00Projected 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.7295% 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 →
±674.9%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, Seabirds in California is projected to stay roughly flat through 2027, near 0.00 (95% range 0.00–0.72). A 5-year backtest shows a typical error of ±674.9%, with 100% of held-out values landing inside the 95% band.19702027
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 →
20230.000.000.72
20240.000.000.72
20250.000.000.72
20260.000.000.72
20270.000.000.72

Member Species In California

Seabirds 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 →
Common MurreAlcidae-98%
Pigeon GuillemotAlcidae-87%
Marbled MurreletAlcidae+14%

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