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Species · Pennsylvania · BBS 2025 Release · 1966–2024

Black-throated Blue Warbler Population Trend in Pennsylvania

All statesForest birds

Black-throated Blue Warbler in Pennsylvania has surged: up 18× on the route-weighted index since 1968.

18×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 →
74Routes 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 Blue Warbler Trends in PennsylvaniaNotable 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 Pennsylvania: up 18× on the route-weighted index since 1968.

Black-throated Blue Warbler Population Forecast in Pennsylvania

If the recent trend holds, Black-throated Blue Warbler in Pennsylvania is projected to rise about 16% by 2029 — from 1.3 in 2024 to a central estimate of 1.5 (95% range 1.2–1.8). A 5-year backtest shows a typical error of ±8.9%, with 100% of held-out values landing inside the 95% band.

+16%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 →
1.5Projected 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 →
1.2–1.895% 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 →
±8.9%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 Pennsylvania is projected to rise about 16% by 2029 — from 1.3 in 2024 to a central estimate of 1.5 (95% range 1.2–1.8). A 5-year backtest shows a typical error of ±8.9%, with 100% 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 →
20251.41.11.7
20261.41.11.8
20271.51.11.8
20281.51.21.8
20291.51.21.8

Black-throated Blue Warbler Survey Routes in Pennsylvania

Routes recording Black-throated Blue Warbler in Pennsylvania.
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 →
Broad Mtn.1620241994
Odin1420241988
Ansonia1020242002
Munson920241994
Sproul Sf-A920242002
Mill Run820241978
Sproul Sf-B820242002
Laurel Hill620241978
Lynch520241970
Eldred520221991
Roulette520211973
English Ctr519891987
Cherry Sprs520231980
Rothrock Sf520191992
Roulette 2520242022
Susquehanna420231981
Ltl Pine Cr420241990
Ellenton320241983
Pottersdale320231991
Betula320222001
Logue320231971
Whig Hill220241966
N Pine Grove220241972
Ridgway220181988
Arnot220152002

Black-throated Blue Warbler Population Trend in Other States

connecticutgeorgiamainemarylandmassachusettsmichiganminnesotanew-hampshirenew-jerseynew-yorknorth-carolinarhode-islandtennesseevermontvirginiawest-virginiawisconsin

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