BirdAnalyst
Species · BBS 2026 Release · 1966–2025

Townsend's Warbler Population Analysis

ParulidaeForest birdsSetophaga townsendi

Townsend's Warbler has surged: up 853% on the route-weighted index since 1970.

+853%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 →
265RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57Years 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 Townsend's Warbler

The Townsend's Warbler (Setophaga townsendi) 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 265 Breeding Bird Survey routes across 6 states, most concentrated in the Northern Rockies.
Family
Parulidae · Forest birds

Notable Townsend's 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 →

Townsend's Warbler has surged in surveyed states: up 852% on the route-weighted index since 1970.

Townsend's Warbler Population Forecast

If the recent trend holds, Townsend's Warbler is projected to rise about 48% by 2030 — from 0.47 in 2025 to a central estimate of 0.70 (95% range 0.53–0.87). A 5-year backtest shows a typical error of ±30.3%, with 60% of held-out values landing inside the 95% band.

+48%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 →
0.70Projected 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 →
0.53–0.8795% 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 →
±30.3%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, Townsend's Warbler is projected to rise about 48% by 2030 — from 0.47 in 2025 to a central estimate of 0.70 (95% range 0.53–0.87). A 5-year backtest shows a typical error of ±30.3%, with 60% 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 →
20260.660.490.83
20270.670.500.84
20280.680.510.85
20290.690.520.86
20300.700.530.87

Where the Townsend's Warbler Is Detected

BBS routes recording Townsend's Warbler, sized by most recent count.

Townsend's Warbler Population Trend by State

Townsend's 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 →
Alaska+115%198272
Idaho+802%197226
Montana+167%197030
Oregon+98%197065
Washington+154%197069
Wyominginsufficient datan/a3

Townsend's Warbler Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Townsend's 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 →
BCR 4+43%198439
Northern Pacific Rainforest15×197090
Great Basin+22%197040
Northern Rockies+207%197095

Townsend's Warbler Conservation Status

Our route-weighted index shows it up about 852% since 1970.

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14. Trend is a route-weighted relative-abundance index, not an absolute population.