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Species · Delaware · BBS 2025 Release · 1966–2024

Black-and-white Warbler Population Trend in Delaware

All statesForest birds

Black-and-white Warbler in Delaware has declined: down 44% on the route-weighted index since 1968.

-44%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 →
33YearsYears 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 →

No notable trend signals for Black-and-white Warbler in Delaware. See the full index history below.

Black-and-white Warbler Population Forecast in Delaware

If the recent trend holds, Black-and-white Warbler in Delaware is projected to fall about 89% by 2029 — from 0.20 in 2024 to a central estimate of 0.02 (95% range 0.00–0.76). A 5-year backtest shows a typical error of ±185.7%, with 80% of held-out values landing inside the 95% band.

-89%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 →
0.02Projected 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 →
0.00–0.7695% 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 →
±185.7%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 89% by 2029 — from 0.20 in 2024 to a central estimate of 0.02 (95% range 0.00–0.76). A 5-year backtest shows a typical error of ±185.7%, with 80% 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 →
20250.060.000.80
20260.050.000.79
20270.040.000.78
20280.030.000.77
20290.020.000.76

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 2120242022

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 2026-05-22.