BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Hermit Warbler

ParulidaeForest birdsSetophaga occidentalis

Hermit Warbler has surged: up 333% on the route-weighted index since 1970.

+333%Since 1970TrendPercent 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 →
195RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
56Years 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 Hermit Warbler

The Hermit Warbler (Setophaga occidentalis) is a North American member of the Wood-Warblers (Parulidae). In this analysis it is grouped with the forest birds.

Size
4.5–5.5 in long (11–14 cm) — a small, active songbird (typical for the family)
Habitat
Woodlands and forest edges, including wooded suburbs and parks.
Diet
Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
Range
Recorded on 195 Breeding Bird Survey routes across 3 states, most concentrated in the Northern Pacific Rainforest.
Family
Parulidae · Forest birds

Notable Hermit Warbler TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc increasecomputed 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 →

Hermit Warbler has surged in surveyed states: up 333% on the route-weighted index since 1970.

Hermit Warbler Population Forecast

If the recent trend holds, Hermit Warbler is projected to rise about 50% by 2029 — from 0.31 in 2024 to a central estimate of 0.46 (95% range 0.27–0.66). A 5-year backtest shows a typical error of ±45.5%, with 100% of held-out values landing inside the 95% band.

+50%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 →
0.46Projected 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 →
0.27–0.6695% 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 →
±45.5%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, Hermit Warbler is projected to rise about 50% by 2029 — from 0.31 in 2024 to a central estimate of 0.46 (95% range 0.27–0.66). A 5-year backtest shows a typical error of ±45.5%, with 100% 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 →
20250.450.250.64
20260.450.250.65
20270.450.260.65
20280.460.260.66
20290.460.270.66

Where the Hermit Warbler Is Detected

BBS routes recording Hermit Warbler, sized by most recent count.

Hermit Warbler Population Trend by State

Hermit Warbler 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 →
California+446%1970109
Oregon+45%197059
Washington+1%197127

Hermit Warbler Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Hermit Warbler 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 Rainforest+57%1970104
Great Basin+14%197324
Sierra Nevada+109%197138
Coastal California+286%197323

Hermit Warbler Conservation Status

Our route-weighted index shows it up about 333% since 1970.

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