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

Least Tern Population Trend in California

All statesWetland birds

Least Tern in California has increased: up 26% on the route-weighted index since 1974.

+26%Since 1974TrendPercent 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 →
5Routes 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 →
12YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Least Tern 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 →

No notable trend signals for Least Tern in California. See the full index history below.

Least Tern Survey Routes in California

Routes recording Least Tern 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 →
Jofegan 21820242024
Poway619801974
Cp. Pendleton519701970
San Ysidro319921973
Niland219821982

Least Tern Population Trend in Other States

alabamaarkansascoloradodelawarefloridageorgiaillinoiskansaskentuckylouisianamainemarylandmassachusettsmississippimissourinebraskanew-jerseynew-yorknorth-carolinaoklahomasouth-carolinatennesseetexasvirginia

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