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Species · Maryland · BBS 2025 Release · 1966–2024

Warbling Vireo Population Trend in Maryland

All statesForest birds

Warbling Vireo in Maryland has surged: up 233% on the route-weighted index since 1968.

+233%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 →
47Routes 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 Warbling Vireo 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 →

Warbling Vireo has surged in Maryland: up 233% on the route-weighted index since 1968.

Warbling Vireo Population Forecast in Maryland

If the recent trend holds, Warbling Vireo in Maryland is projected to fall about 22% by 2029 — from 0.93 in 2024 to a central estimate of 0.72 (95% range 0.47–0.98). A 5-year backtest shows a typical error of ±27.1%, with 40% of held-out values landing inside the 95% band.

-22%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 →
0.72Projected 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 →
0.47–0.9895% 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 →
±27.1%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, Warbling Vireo in Maryland is projected to fall about 22% by 2029 — from 0.93 in 2024 to a central estimate of 0.72 (95% range 0.47–0.98). A 5-year backtest shows a typical error of ±27.1%, with 40% 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 →
20250.690.430.94
20260.690.440.95
20270.700.450.96
20280.710.460.97
20290.720.470.98

Warbling Vireo Survey Routes in Maryland

Routes recording Warbling Vireo 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 →
Earlton1620242014
Smithsburg620141967
Emmitsburg620241967
Fair Hill519961992
Williamsport420241974
Berlin320052005
Madonna320222009
Floyd220052005
Olney220241970
Bachman Mill220241996
Randallstown220131971
Upper Xrds220061966
Van Bibber220111966
Northeast220081966
Piney Neck220221967
Ijamsville220241986
Oldtown120241977
Potomac Park120241970
Wolfsville120241977
Silver Spg119791979
Norwood119781969
Warfieldsbrg120231967
Pleasant Val120241975
Fowblesburg120161972
Eklo120141988

Warbling Vireo Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawareidahoillinoisindianaiowakansaskentuckylouisianamainemassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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