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

Purple Martin Population Trend in California

All statesAerial insectivores

Purple Martin in California has fallen sharply: down 57% on the route-weighted index since 1970.

-57%Since 1970TrendPercent 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 →
53Routes 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 →
56YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Purple Martin Trends in CaliforniaNotable 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 declinecomputed 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 →

Purple Martin has fallen sharply in California: down 57% on the route-weighted index since 1970.

Purple Martin Population Forecast in California

If the recent trend holds, Purple Martin in California is projected to fall about 25% by 2029 — from 0.21 in 2024 to a central estimate of 0.16 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±33.9%, with 100% of held-out values landing inside the 95% band.

-25%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 →
0.16Projected 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 →
0.00–0.3595% 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 →
±33.9%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, Purple Martin in California is projected to fall about 25% by 2029 — from 0.21 in 2024 to a central estimate of 0.16 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±33.9%, 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 →
20250.170.000.36
20260.170.000.36
20270.170.000.35
20280.160.000.35
20290.160.000.35

Purple Martin Survey Routes in California

Routes recording Purple Martin in California.
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 →
Alderpoint1320121983
Holmes820131970
Glen Ellen819971992
Creston720241973
Fish Rock520141968
Longvale520131977
Point Reyes520231970
Navarro520112000
Nubieber420172016
Crescent Cty420241977
Santa Ynez420021981
Waterman Gap420242017
Rio Dell420111972
Fairfax420241972
Iron Gate320191991
Cottage Spgs319721972
Bodega Bay319731972
Greenfield320212018
Cleveland Nf 2320222022
Carmel Val320232014
Mt Laguna319741974
Eagle Lake220021970
Tres Pinos219811968
Parkfield219681968
Junction Cty219841972

Purple Martin Population Trend in Other States

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

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