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Species · Maryland · BBS 2025 Release · 1966–2024

Worm-eating Warbler Population Trend in Maryland

All statesForest birds

Worm-eating Warbler in Maryland has surged: up 699% on the route-weighted index since 1968.

+699%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 →
64Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Worm-eating Warbler Trends in MarylandNotable 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 →

Worm-eating Warbler has surged in Maryland: up 699% on the route-weighted index since 1968.

Worm-eating Warbler Population Forecast in Maryland

If the recent trend holds, Worm-eating Warbler in Maryland is projected to fall about 15% by 2029 — from 2.1 in 2024 to a central estimate of 1.8 (95% range 1.2–2.4). A 5-year backtest shows a typical error of ±39.7%, with 0% of held-out values landing inside the 95% band.

-15%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 →
1.8Projected 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 →
1.2–2.495% 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 →
±39.7%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, Worm-eating Warbler in Maryland is projected to fall about 15% by 2029 — from 2.1 in 2024 to a central estimate of 1.8 (95% range 1.2–2.4). A 5-year backtest shows a typical error of ±39.7%, with 0% 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 →
20251.71.12.3
20261.71.22.3
20271.81.22.3
20281.81.22.3
20291.81.22.4

Worm-eating Warbler Survey Routes in Maryland

Routes recording Worm-eating Warbler in Maryland.
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 →
Piney Grove2120241995
Oldtown1820241970
Berlin1020241980
Furnace Town920242015
Green Ridge620241995
Madison520241969
Cokesbury520241969
Eklo420171979
Walnut420242001
Island Creek420241992
Indiantown320141977
Earlton320242014
Floyd220171967
Potomac Park220231971
Van Bibber220131967
Snow Hill219761968
Madonna220172009
Davidsnville220211985
Mt Nebo119911972
Vindex119841967
Williamsport120172017
Smithsburg120131972
Wolfsville120111966
Bald Friar119941993
Olney120231995

Worm-eating Warbler Population Trend in Other States

alabamaarkansasconnecticutdelawaregeorgiaillinoisindianaiowakentuckylouisianamassachusettsmississippimissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvirginiawest-virginiawisconsin

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.