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Species · Alaska · BBS 2025 Release · 1966–2024

Tree Swallow Population Trend in Alaska

All statesAerial insectivores

Tree Swallow in Alaska has surged: up 90% on the route-weighted index since 1973.

+90%Since 1973TrendPercent 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 →
115Routes 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 →
50YearsYears 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 AlaskaNotable 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 Alaska: up 90% on the route-weighted index since 1973.

Tree Swallow Population Forecast in Alaska

If the recent trend holds, Tree Swallow in Alaska is projected to fall about 51% by 2029 — from 2.1 in 2024 to a central estimate of 1.0 (95% range 0.00–6.3). A 5-year backtest shows a typical error of ±39%, with 100% of held-out values landing inside the 95% band.

-51%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 →
1.0Projected 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 →
0.00–6.395% 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 →
±39%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 Alaska is projected to fall about 51% by 2029 — from 2.1 in 2024 to a central estimate of 1.0 (95% range 0.00–6.3). A 5-year backtest shows a typical error of ±39%, 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 →
20251.40.006.6
20261.30.006.5
20271.20.006.4
20281.10.006.3
20291.00.006.3

Tree Swallow Survey Routes in Alaska

Routes recording Tree Swallow in Alaska.
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 →
Togiak River9120051994
Tupuknuk5519951995
Kanektok Riv5420051995
Wasilla4219831983
Moose Pass3919851983
Dillingham3720191993
King Salmon3620241993
Cottonwood3619901987
Cordova2420241983
Skilak Lake2119851977
Goose Bay2019821975
Sitka (Short)1919921984
Gweek River1520021994
Goodnews Bay1220052000
Unalakleet River1220231998
Galena (Short)1120241985
Hather Creek1120241993
Matanuska1019831982
Chena Hot Sp919901986
Dillingham (Short)919841984
Juneau820241983
Willow720241993
Sitka720241993
Kotzebue720242001
Copper River620111993

Tree Swallow Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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