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Species · Delaware · BBS 2026 Release · 1966–2025

Black-and-white Warbler Population Trend in Delaware

All statesForest birds

Black-and-white Warbler in Delaware has fallen sharply: down 52% on the route-weighted index since 1968.

-52%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 →
12Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
34YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black-and-white Warbler Trends in DelawareNotable 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 declinecomputed 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 →

Black-and-white Warbler has fallen sharply in Delaware: down 52% on the route-weighted index since 1968.

Black-and-white Warbler Population Forecast in Delaware

If the recent trend holds, Black-and-white Warbler in Delaware is projected to fall about 86% by 2030 — from 0.17 in 2025 to a central estimate of 0.02 (95% range 0.00–0.75). A 5-year backtest shows a typical error of ±189.9%, with 80% of held-out values landing inside the 95% band.

-86%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 →
0.02Projected 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 →
0.00–0.7595% 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 →
±189.9%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, Black-and-white Warbler in Delaware is projected to fall about 86% by 2030 — from 0.17 in 2025 to a central estimate of 0.02 (95% range 0.00–0.75). A 5-year backtest shows a typical error of ±189.9%, with 80% of held-out values landing inside the 95% band.19662030
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 →
20260.060.000.79
20270.050.000.78
20280.040.000.77
20290.030.000.76
20300.020.000.75

Black-and-white Warbler Survey Routes in Delaware

Routes recording Black-and-white Warbler in Delaware.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Lowes Xrds219911966
Bethany Bch219661966
Millsboro220172017
Pepperbox220161999
Mt Pleasant119841966
Harrington119681968
Frederica120121966
Frankford119931966
Holleyville120031966
Milton119751970
Georgetown119971992
Pepperbox 2120252022

Black-and-white Warbler Population Trend in Other States

alabamaarkansascaliforniaconnecticutgeorgiaillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.