BirdAnalyst
Species · West Virginia · BBS 2025 Release · 1966–2024

Tree Swallow Population Trend in West Virginia

All statesAerial insectivores

Tree Swallow in West Virginia has surged: up 23× on the route-weighted index since 1977.

23×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 →
59Routes 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 →
47YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Tree Swallow Trends in West VirginiaNotable 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 West Virginia: up 23× on the route-weighted index since 1977.

Tree Swallow Population Forecast in West Virginia

If the recent trend holds, Tree Swallow in West Virginia is projected to rise about 72% by 2029 — from 2.3 in 2024 to a central estimate of 3.9 (95% range 2.6–5.3). A 5-year backtest shows a typical error of ±74.3%, with 40% of held-out values landing inside the 95% band.

+72%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 →
3.9Projected 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 →
2.6–5.395% 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 →
±74.3%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 West Virginia is projected to rise about 72% by 2029 — from 2.3 in 2024 to a central estimate of 3.9 (95% range 2.6–5.3). A 5-year backtest shows a typical error of ±74.3%, with 40% of held-out values landing inside the 95% band.19742029
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 →
20253.62.25.0
20263.72.35.0
20273.82.45.1
20283.82.55.2
20293.92.65.3

Tree Swallow Survey Routes in West Virginia

Routes recording Tree Swallow in West Virginia.
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 →
Welch3520222002
Clear Creek2620241995
Ghent1320241990
Clendenin1320242003
Glade Run919991999
Lost River720232001
Hubbardstown620232003
Ruthbelle620241975
Pt Pleasant520222000
Spencer520232004
Yellow Spg520221984
Shanghai520221999
Stollings420072004
Bramwell420191981
Yawkey420242003
Washburn420152002
Paradise320231995
Olcott320241995
Slate320242011
Hix220241986
Smoot220191986
Meadland220182002
Nicut220241989
Fayetteville219961991
Sutton220221989

Tree Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwisconsinwyoming

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