BirdAnalyst
Species · BCR 29 · BBS 2025 Release · 1966–2024

Warbling Vireo In Piedmont

All regionsPiedmontForest birds

Warbling Vireo in Piedmont has surged: up 198% on the route-weighted index since 1968.

+198%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 →
56Routes In RegionSurvey 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 SignalsNotable 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 Piedmont: up 198% on the route-weighted index since 1968.

Warbling Vireo In Piedmont Population Forecast

If the recent trend holds, Warbling Vireo in Piedmont is projected to fall about 24% by 2029 — from 0.59 in 2024 to a central estimate of 0.45 (95% range 0.25–0.64). A 5-year backtest shows a typical error of ±24.9%, with 100% of held-out values landing inside the 95% band.

-24%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 →
0.45Projected 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 →
0.25–0.6495% 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 →
±24.9%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, Warbling Vireo in Piedmont is projected to fall about 24% by 2029 — from 0.59 in 2024 to a central estimate of 0.45 (95% range 0.25–0.64). A 5-year backtest shows a typical error of ±24.9%, 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 →
20250.430.240.63
20260.440.240.63
20270.440.240.64
20280.440.250.64
20290.450.250.64

Routes In Piedmont

Routes recording Warbling Vireo in Piedmont.
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 →
EarltonMARYLAND162024
West GrovePENNSYLVANIA111996
EmmitsburgMARYLAND62024
Mount JoyPENNSYLVANIA52024
ChathamPENNSYLVANIA42024
MadonnaMARYLAND32022
JacobusPENNSYLVANIA32024
TaylorstownVIRGINIA32007
Taylorstown 2VIRGINIA32024
OlneyMARYLAND22024
Bachman MillMARYLAND22024
RandallstownMARYLAND22013
Upper XrdsMARYLAND22006
Van BibberMARYLAND22011
IjamsvilleMARYLAND22024
CollegevillePENNSYLVANIA22024
AspersPENNSYLVANIA21973
BendersvillePENNSYLVANIA22024
Silver SpgMARYLAND11979
NorwoodMARYLAND11978
WarfieldsbrgMARYLAND12023
Pleasant ValMARYLAND12024
FowblesburgMARYLAND12016
EkloMARYLAND12014
TheodoreMARYLAND12016

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