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Species · Maryland · BBS 2025 Release · 1966–2024

Black-throated Blue Warbler Population Trend in Maryland

All statesForest birds

Black-throated Blue Warbler in Maryland has surged: up 578% on the route-weighted index since 1968.

+578%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 →
9Routes 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 →
53YearsYears 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 Blue 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 Blue Warbler has surged in Maryland: up 578% on the route-weighted index since 1968.

Black-throated Blue Warbler Population Forecast in Maryland

If the recent trend holds, Black-throated Blue Warbler in Maryland is projected to rise about 102% by 2029 — from 0.17 in 2024 to a central estimate of 0.34 (95% range 0.19–0.49). A 5-year backtest shows a typical error of ±76.4%, with 20% of held-out values landing inside the 95% band.

+102%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 →
0.34Projected 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 →
0.19–0.4995% 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 →
±76.4%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 Blue Warbler in Maryland is projected to rise about 102% by 2029 — from 0.17 in 2024 to a central estimate of 0.34 (95% range 0.19–0.49). A 5-year backtest shows a typical error of ±76.4%, with 20% 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 →
20250.310.160.47
20260.320.170.47
20270.330.170.48
20280.330.180.48
20290.340.190.49

Black-throated Blue Warbler Survey Routes in Maryland

Routes recording Black-throated Blue 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 →
Jennings520241995
Accident 2420212018
Accident320171993
Floyd220221966
Potomac Park219711971
Finzel220241995
Mt Nebo119881972
Vindex120211968
Steyer120022002

Black-throated Blue Warbler Population Trend in Other States

connecticutgeorgiamainemassachusettsmichiganminnesotanew-hampshirenew-jerseynew-yorknorth-carolinapennsylvaniarhode-islandtennesseevermontvirginiawest-virginiawisconsin

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