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Species · Pennsylvania · BBS 2025 Release · 1966–2024

Warbling Vireo Population Trend in Pennsylvania

All statesForest birds

Warbling Vireo in Pennsylvania has surged: up 181% on the route-weighted index since 1968.

+181%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 →
114Routes 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 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 →

Warbling Vireo has surged in Pennsylvania: up 181% on the route-weighted index since 1968.

Warbling Vireo Population Forecast in Pennsylvania

If the recent trend holds, Warbling Vireo in Pennsylvania is projected to stay roughly flat through 2029, near 1.4 (95% range 1.1–1.8). A 5-year backtest shows a typical error of ±9.7%, with 100% 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 →
1.4Projected 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 →
1.1–1.895% 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 →
±9.7%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 →
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 →
20251.41.01.7
20261.41.01.8
20271.41.11.8
20281.41.11.8
20291.41.11.8

Warbling Vireo Survey Routes in Pennsylvania

Routes recording Warbling Vireo 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 →
Harmonsburg2420231966
West Grove1119961967
Greentown920241970
Ferris Crnrs820241967
Waterstreet720241982
Akeley619761966
Betula520221974
Susquehanna520241971
Beaver520242008
Geeseytown520241987
Sugar Grove520241984
Mount Joy520241988
Austinville420241982
Jefferson420241966
Harrisville420232005
Ltl Pine Cr420241993
Schaefferstown 2420212011
Drehersville 2420242000
Chatham420241997
Little Marsh320241993
Millville320241986
Normalville319731973
Jacobus320241986
Espyville220241971
Odin220132013

Warbling Vireo Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawareidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonrhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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