BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Marbled Murrelet

AlcidaeSeabirdsBrachyramphus marmoratus

Marbled Murrelet has surged: up 31× on the route-weighted index since 1977.

31×Since 1977TrendPercent 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 →
40RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
46Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Marbled Murrelet

The Marbled Murrelet (Brachyramphus marmoratus) is a North American member of the Auks, Murres & Puffins (Alcidae). In this analysis it is grouped with the seabirds.

Size
8–17.5 in long (20–45 cm) — a compact seabird (typical for the family)
Habitat
Open ocean and coastlines, coming ashore mainly to nest in colonies.
Diet
Fish, squid and other marine animals caught at or below the surface.
Range
Recorded on 40 Breeding Bird Survey routes across 4 states, most concentrated in the Northern Pacific Rainforest.
Family
Alcidae · Seabirds

Notable Marbled Murrelet TrendsNotable 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 Marbled Murrelet. See the full index history below.

Marbled Murrelet Population Forecast

If the recent trend holds, Marbled Murrelet is projected to fall about 43% by 2029 — from 0.08 in 2024 to a central estimate of 0.05 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±91.8%, with 100% of held-out values landing inside the 95% band.

-43%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 →
0.05Projected 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 →
0.00–0.1395% 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 →
±91.8%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, Marbled Murrelet is projected to fall about 43% by 2029 — from 0.08 in 2024 to a central estimate of 0.05 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±91.8%, with 100% of held-out values landing inside the 95% band.19722029
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 →
20250.050.000.13
20260.050.000.13
20270.050.000.13
20280.050.000.13
20290.050.000.13

Where the Marbled Murrelet Is Detected

BBS routes recording Marbled Murrelet, sized by most recent count.

Marbled Murrelet Population Trend by State

Marbled Murrelet population trend by state.
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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alaska+97%197726
California+14%19856
Oregoninsufficient datan/a4
Washington-88%19874

Marbled Murrelet Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Marbled Murrelet population trend by Bird Conservation Region.
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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Northern Pacific Rainforest26×197736

Marbled Murrelet Conservation Status

Our route-weighted index shows it up about 3045% since 1977.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.