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Species · Maryland · BBS 2025 Release · 1966–2024

Black-throated Green Warbler Population Trend in Maryland

All statesForest birds

Black-throated Green Warbler in Maryland has surged: up 17× on the route-weighted index since 1968.

17×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 →
13Routes 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 Black-throated Green 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 →

Black-throated Green Warbler has surged in Maryland: up 17× on the route-weighted index since 1968.

Black-throated Green Warbler Population Forecast in Maryland

If the recent trend holds, Black-throated Green Warbler in Maryland is projected to stay roughly flat through 2029, near 1.0 (95% range 0.66–1.4). A 5-year backtest shows a typical error of ±30.5%, with 60% of held-out values landing inside the 95% band.

+2%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 →
1.0Projected 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 →
0.66–1.495% 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 →
±30.5%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-throated Green Warbler in Maryland is projected to stay roughly flat through 2029, near 1.0 (95% range 0.66–1.4). A 5-year backtest shows a typical error of ±30.5%, with 60% 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 →
20250.940.581.3
20260.960.601.3
20270.980.621.3
20281.00.641.4
20291.00.661.4

Black-throated Green Warbler Survey Routes in Maryland

Routes recording Black-throated Green 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 →
Finzel2720241995
Jennings1320241995
Vindex320191966
Accident 2220242018
Steyer220191996
Floyd120231967
Mt Nebo119911969
Oldtown120051976
Potomac Park120232023
Accident120171992
Smithsburg119981998
Green Ridge120092009
Severna Park120002000

Black-throated Green Warbler Population Trend in Other States

alabamaarkansasconnecticutgeorgiaindianakentuckymainemassachusettsmichiganminnesotamissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseevermontvirginiawest-virginiawisconsin

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