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Species · Pennsylvania · BBS 2026 Release · 1966–2025

Black-throated Blue Warbler Population Trend in Pennsylvania

All statesForest birds

Black-throated Blue Warbler in Pennsylvania 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 →
75Routes 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 →
59YearsYears 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 17× 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 31% by 2030 — from 1.2 in 2025 to a central estimate of 1.5 (95% range 1.2–1.9). A 5-year backtest shows a typical error of ±10.2%, with 100% of held-out values landing inside the 95% band.

+31%Change by 2030TrendPercent 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 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
1.2–1.995% 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 →
±10.2%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 31% by 2030 — from 1.2 in 2025 to a central estimate of 1.5 (95% range 1.2–1.9). A 5-year backtest shows a typical error of ±10.2%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20261.41.11.8
20271.41.11.8
20281.51.11.8
20291.51.21.8
20301.51.21.9

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 →
Lynch1420251970
Broad Mtn.920251994
Laurel Hill820251978
Odin720251988
Ltl Pine Cr720251990
N Pine Grove620251972
Eldred520221991
Roulette520211973
English Ctr519891987
Rothrock Sf520191992
Logue420251971
Cherry Sprs420251980
Pocono Summit420251967
Susquehanna420231981
Munson420251994
Sproul Sf-A420252002
Pottersdale320251991
Betula320222001
Marsh Hill320251983
Mill Run320251978
Ansonia320252002
Ellenton220251983
Whig Hill220251966
Wild Creek220251988
Ridgway220181988

Black-throated Blue Warbler Population Trend in Other States

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

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.