BirdAnalyst
Species · California · BBS 2025 Release · 1966–2024

Tree Swallow Population Trend in California

All statesAerial insectivores

Tree Swallow in California has risen sharply: up 63% on the route-weighted index since 1970.

+63%Since 1970
173Routes In State
56Years

Notable Tree Swallow Trends in California

long arc increasecomputed index

Tree Swallow has risen sharply in California: up 63% on the route-weighted index since 1970.

Tree Swallow Population Forecast in California

If the recent trend holds, Tree Swallow in California is projected to rise about 26% by 2029 — from 2.8 in 2024 to a central estimate of 3.6 (95% range 1.9–5.2). A 5-year backtest shows a typical error of ±84.7%, with 40% of held-out values landing inside the 95% band.

+26%Change by 2029
3.6Projected 2029 index
1.9–5.295% range
±84.7%Backtest error
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 index95% low95% high
20253.51.85.1
20263.51.95.1
20273.51.95.2
20283.61.95.2
20293.61.95.2

Tree Swallow Survey Routes in California

Routes recording Tree Swallow in California.
Oroville8920241972
Horse Creek7020191970
Glenn7020231975
Auburn4119801969
Moraga3620241995
El Toro2319841973
Coyote2020241974
Ono1820121984
Honeydew1620171969
Orleans 21620142014
Orland1420221974
Bodega Bay1420111972
Cordova1319801972
Crescent Cty1120241972
Bass Lake1120181973
Yokohl Val1119971972
Copperopolis1120241979
Yreka1020191973
Tres Pinos 21020102007
Glen Ellen 21020232009
Burnt Ranch1020162008
Coalinga920221980
Zamora920241980
Hackamore920102001
Holmes820221969

Tree Swallow Population Trend in Other States

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

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