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

Tree Swallow In Piedmont

All regionsPiedmontAerial insectivores

Tree Swallow in Piedmont has surged: up 34× on the route-weighted index since 1971.

34×Since 1971TrendPercent 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 →
103Routes 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 →
55YearsYears 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 →

Tree Swallow has surged in Piedmont: up 34× on the route-weighted index since 1971.

Tree Swallow In Piedmont Population Forecast

If the recent trend holds, Tree Swallow in Piedmont is projected to rise about 45% by 2029 — from 1.3 in 2024 to a central estimate of 1.8 (95% range 1.3–2.4). A 5-year backtest shows a typical error of ±32.8%, with 80% of held-out values landing inside the 95% band.

+45%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 →
1.8Projected 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 →
1.3–2.495% 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 →
±32.8%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, Tree Swallow in Piedmont is projected to rise about 45% by 2029 — from 1.3 in 2024 to a central estimate of 1.8 (95% range 1.3–2.4). A 5-year backtest shows a typical error of ±32.8%, with 80% of held-out values landing inside the 95% band.19692029
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 →
20251.71.12.3
20261.71.22.3
20271.81.22.3
20281.81.22.4
20291.81.32.4

Routes In Piedmont

Routes recording Tree Swallow 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 →
EarltonMARYLAND122024
Lake AnnaVIRGINIA122024
Doe RunPENNSYLVANIA112024
Van BibberMARYLAND82013
AppomattoxVIRGINIA82023
AkronPENNSYLVANIA71997
SiloamNORTH-CAROLINA62024
Mt GretnaPENNSYLVANIA62000
Mount JoyPENNSYLVANIA62024
DavidVIRGINIA62012
AmherstVIRGINIA62024
ElamsvilleVIRGINIA62016
GladysVIRGINIA62021
WarfieldsbrgMARYLAND52023
JacobusPENNSYLVANIA52024
LeolaPENNSYLVANIA52024
ProsperitySOUTH-CAROLINA52010
Carters BrdgVIRGINIA52014
Brandy StationVIRGINIA52024
EmmitsburgMARYLAND42024
EkloMARYLAND42017
SheffieldNORTH-CAROLINA42023
BullockNORTH-CAROLINA42023
Big IslandVIRGINIA42024
Silver SpgMARYLAND31982

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