BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Wilson's Warbler

ParulidaeForest birdsCardellina pusilla

Wilson's Warbler has surged: up 746% on the route-weighted index since 1968.

+746%Since 1968TrendPercent 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 →
787RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58Years 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 Wilson's Warbler

The Wilson's Warbler (Cardellina pusilla) 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 787 Breeding Bird Survey routes across 18 states, most concentrated in the Northern Pacific Rainforest.
Family
Parulidae · Forest birds

Notable Wilson'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 →

Wilson's Warbler has surged in surveyed states: up 746% on the route-weighted index since 1968.

Wilson's Warbler Population Forecast

If the recent trend holds, Wilson's Warbler is projected to rise about 46% by 2029 — from 0.79 in 2024 to a central estimate of 1.1 (95% range 0.80–1.5). A 5-year backtest shows a typical error of ±45.3%, with 20% of held-out values landing inside the 95% band.

+46%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 →
1.1Projected 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 →
0.80–1.595% 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 →
±45.3%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, Wilson's Warbler is projected to rise about 46% by 2029 — from 0.79 in 2024 to a central estimate of 1.1 (95% range 0.80–1.5). A 5-year backtest shows a typical error of ±45.3%, with 20% of held-out values landing inside the 95% band.19662029
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 →
20251.10.751.4
20261.10.761.4
20271.10.771.5
20281.10.791.5
20291.10.801.5

Where the Wilson's Warbler Is Detected

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

Wilson's Warbler Population Trend by State

Wilson'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+4%1972129
California-57%1970168
Colorado-8%197072
Idaho+152%197538
Maine-84%196943
Michiganinsufficient datan/a6
Minnesota-20%198613
Montana-18%197239
Nevada-21%199316
New Hampshire-68%19688
New Mexicoinsufficient datan/a8
New York+65%19803
Oregon+32%197091
Utah-81%197729
Vermontinsufficient datan/a3
Washington-32%197084
Wisconsininsufficient datan/a1
Wyoming-49%197036

Wilson's Warbler Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Wilson'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 2-48%198523
BCR 3+59%19984
BCR 4+22%197868
Northern Pacific Rainforest-5%1970157
Great Basin+9%1970110
Northern Rockies-2%1970123
Boreal Hardwood Transition-20%198620
Atlantic Northern Forest-91%196857
Sierra Nevada-55%197033
Southern Rockies / Colorado Plateau+65%1970103
Coastal California+106%197177
Sonoran and Mojave Deserts-49%19736

Wilson's Warbler Conservation Status

Our route-weighted index shows it up about 746% since 1968.

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