BirdAnalyst
Species · BBS 2025 Release · 1966–2024

American Tree Sparrow

PasserellidaeForest birdsSpizelloides arborea

American Tree Sparrow has surged: up 93× on the route-weighted index since 1977.

93×Since 1977TrendPercent 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 →
73RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
45Years 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 American Tree Sparrow

The American Tree Sparrow (Spizelloides arborea) is a North American member of the New World Sparrows (Passerellidae). In this analysis it is grouped with the forest birds.

Size
4.5–7.5 in long (12–19 cm) — a small 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 73 Breeding Bird Survey routes across 1 state, most concentrated in the BCR 4.
Family
Passerellidae · Forest birds

Notable American Tree Sparrow 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 American Tree Sparrow. See the full index history below.

American Tree Sparrow Population Forecast

If the recent trend holds, American Tree Sparrow is projected to rise about 15% by 2029 — from 0.22 in 2024 to a central estimate of 0.26 (95% range 0.12–0.40). A 5-year backtest shows a typical error of ±16.2%, with 100% of held-out values landing inside the 95% band.

+15%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 →
0.26Projected 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 →
0.12–0.4095% 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 →
±16.2%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, American Tree Sparrow is projected to rise about 15% by 2029 — from 0.22 in 2024 to a central estimate of 0.26 (95% range 0.12–0.40). A 5-year backtest shows a typical error of ±16.2%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20250.240.100.39
20260.250.100.39
20270.250.110.39
20280.250.110.40
20290.260.120.40

Where the American Tree Sparrow Is Detected

BBS routes recording American Tree Sparrow, sized by most recent count.

American Tree Sparrow Population Trend by State

American Tree Sparrow 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 →
Alaska+518%197773

American Tree Sparrow Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

American Tree Sparrow 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 →
BCR 2+49%198719
BCR 3+347%19964
BCR 4+227%197744
Northern Pacific Rainforest-92%19856

American Tree Sparrow Conservation Status

Our route-weighted index shows it up about 9224% since 1977.

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