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

Caspian Tern Population Trend in California

All statesWetland birds

Caspian Tern in California has declined: down 33% on the route-weighted index since 1970.

-33%Since 1970
54Routes In State
55Years

Notable Caspian Tern Trends in California

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

Caspian Tern Population Forecast in California

If the recent trend holds, Caspian Tern in California is projected to rise about 222% by 2029 — from 0.21 in 2024 to a central estimate of 0.69 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±1159.6%, with 20% of held-out values landing inside the 95% band.

+222%Change by 2029
0.69Projected 2029 index
0.00–1.495% range
±1159.6%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
20250.670.001.4
20260.670.001.4
20270.680.001.4
20280.690.001.4
20290.690.001.4

Caspian Tern Survey Routes in California

Routes recording Caspian Tern in California.
Iron Gate7920191988
Harbor Lake 21520242014
Dorris1120191972
Adelaida819921992
Colma619721968
Ingalls519991974
Alamo River519861986
Honeydew420111968
Cedarville319981998
Fish Rock220131977
Collegeville219771977
Brawley220122007
Westley220181993
Honey Lake219761973
Foster Park219741974
Moraga220191974
Clear Lk Res220181972
S Catalina220172013
Buena Vista220191993
Nubieber119991989
Eagle Lake120071980
Pennington119781978
Riovista120242024
Shafter119871987
Hughson120102010

Caspian Tern Population Trend in Other States

alabamaalaskadelawarefloridaidahoillinoisindianalouisianamarylandmichiganminnesotamontananevadanorth-carolinanorth-dakotaoregonsouth-carolinatexasutahvermontvirginiawashingtonwisconsinwyoming

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