BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Philadelphia Vireo

VireonidaeForest birdsVireo philadelphicus

Philadelphia Vireo has held roughly steady: down 4% on the route-weighted index since 1969.

-4%Since 1969TrendPercent 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 →
113RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Philadelphia Vireo

The Philadelphia Vireo (Vireo philadelphicus) is a North American member of the Vireos (Vireonidae). In this analysis it is grouped with the forest birds.

Size
4.5–6 in long (11–15 cm) — a small, deliberate songbird (typical for the family)
Habitat
Woodlands and forest edges, including wooded suburbs and parks.
Diet
Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
Range
Recorded on 113 Breeding Bird Survey routes across 9 states, most concentrated in the Atlantic Northern Forest.
Family
Vireonidae · Forest birds

Notable Philadelphia Vireo TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Philadelphia Vireo. See the full index history below.

Philadelphia Vireo Population Forecast

If the recent trend holds, Philadelphia Vireo is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.01). A 5-year backtest shows a typical error of ±321.7%, with 60% of held-out values landing inside the 95% band.

n/aChange 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 →
0.01Projected 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 →
0.00–0.0195% 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 →
±321.7%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 →
If the recent trend holds, Philadelphia Vireo is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.01). A 5-year backtest shows a typical error of ±321.7%, with 60% of held-out values landing inside the 95% band.19672029
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 →
20250.010.000.01
20260.010.000.01
20270.010.000.01
20280.010.000.01
20290.010.000.01

Where the Philadelphia Vireo Is Detected

BBS routes recording Philadelphia Vireo, sized by most recent count.

Philadelphia Vireo Population Trend by State

Philadelphia Vireo population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alabamainsufficient datan/a1
Maine+109%197244
Michigan+131%199312
Minnesota-73%197316
New Hampshire+9%196912
New York+75%197215
North Dakotainsufficient datan/a1
Vermontinsufficient datan/a7
Wisconsininsufficient datan/a5

Philadelphia Vireo Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Philadelphia Vireo population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Boreal Hardwood Transition-56%197331
Atlantic Northern Forest+32%196977

Philadelphia Vireo Conservation Status

Our route-weighted index shows it down about 4% since 1969.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.