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Species · Delaware · BBS 2026 Release · 1966–2025

Brown Thrasher Population Trend in Delaware

All statesForest birds

Brown Thrasher in Delaware has risen sharply: up 60% on the route-weighted index since 1968.

+60%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 →
17Routes 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 →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Brown Thrasher 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 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 →

Brown Thrasher has risen sharply in Delaware: up 60% on the route-weighted index since 1968.

Brown Thrasher Population Forecast in Delaware

If the recent trend holds, Brown Thrasher in Delaware is projected to fall about 55% by 2030 — from 5.3 in 2025 to a central estimate of 2.4 (95% range 0.32–4.5). A 5-year backtest shows a typical error of ±56%, with 40% of held-out values landing inside the 95% band.

-55%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 →
2.4Projected 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 →
0.32–4.595% 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 →
±56%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, Brown Thrasher in Delaware is projected to fall about 55% by 2030 — from 5.3 in 2025 to a central estimate of 2.4 (95% range 0.32–4.5). A 5-year backtest shows a typical error of ±56%, with 40% 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 →
20262.40.354.5
20272.40.344.5
20282.40.344.5
20292.40.334.5
20302.40.324.5

Brown Thrasher Survey Routes in Delaware

Routes recording Brown Thrasher 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 →
Blackbird1020251994
Frederica620251966
Milton 2520252017
Pepperbox 2520252017
Harrington420251966
Holleyville 2420242006
Dover219871966
Holleyville220041966
Bethany Bch219901966
Millsboro220252017
Pepperbox220081998
Mt Pleasant120191966
Wilmington120141966
Frankford120121966
Lowes Xrds119801966
Milton120161967
Georgetown120221992

Brown Thrasher Population Trend in Other States

alabamaarkansascoloradoconnecticutfloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

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