BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Forster's Tern In Coastal California

All regionsCoastal CaliforniaWetland birds

Forster's Tern in Coastal California has fallen sharply: down 60% on the route-weighted index since 1970.

-60%Since 1970
18Routes In Region
51Years

Notable Signals

long arc declinecomputed index

Forster's Tern has fallen sharply in Coastal California: down 60% on the route-weighted index since 1970.

Forecast

If the recent trend holds, Forster's Tern in Coastal California is projected to stay roughly flat through 2029, near 0.20 (95% range 0.00–0.53). A 5-year backtest shows a typical error of ±534.4%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2029
0.20Projected 2029 index
0.00–0.5395% range
±534.4%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
20250.200.000.53
20260.200.000.53
20270.200.000.53
20280.200.000.53
20290.200.000.53

Routes In Coastal California

Routes recording Forster's Tern in Coastal California.
OrovilleCALIFORNIA302013
PowayCALIFORNIA211978
Carrizo PlnCALIFORNIA151991
CollegevilleCALIFORNIA81987
FairfaxCALIFORNIA61991
ReddingCALIFORNIA41975
CopperopolisCALIFORNIA42001
Foster ParkCALIFORNIA21990
HollisterCALIFORNIA22003
CoyoteCALIFORNIA22014
HughsonCALIFORNIA12024
MorenoCALIFORNIA12024
San YsidroCALIFORNIA12003
SangerCALIFORNIA12013
GlennCALIFORNIA11983
CordovaCALIFORNIA11981
WestleyCALIFORNIA12003
Staten Is.CALIFORNIA12014

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