BirdAnalyst
Species · BCR 9 · BBS 2025 Release · 1966–2024

Forster's Tern In Great Basin

All regionsGreat BasinWetland birds

Forster's Tern in Great Basin has increased: up 31% on the route-weighted index since 1970.

+31%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 →
58Routes In RegionSurvey 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 SignalsNotable 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 Forster's Tern in Great Basin. See the full index history below.

Forster's Tern In Great Basin Population Forecast

If the recent trend holds, Forster's Tern in Great Basin is projected to rise about 309% by 2029 — from 0.11 in 2024 to a central estimate of 0.47 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±166.7%, with 100% of held-out values landing inside the 95% band.

+309%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 →
0.47Projected 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 →
0.00–1.595% 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 →
±166.7%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, Forster's Tern in Great Basin is projected to rise about 309% by 2029 — from 0.11 in 2024 to a central estimate of 0.47 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±166.7%, 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 →
20250.520.001.5
20260.510.001.5
20270.490.001.5
20280.480.001.5
20290.470.001.5

Routes In Great Basin

Routes recording Forster's Tern in Great Basin.
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 →
DorrisCALIFORNIA682019
Bear RiverUTAH352023
Fish LakeOREGON142024
PrincetonOREGON111985
Glenns FerryIDAHO101968
Lapham Res.OREGON102022
Malheur NwrOREGON101992
PrestonIDAHO92004
MacdoelCALIFORNIA72018
Blizzard GapOREGON72023
Trout CreekOREGON72000
Columbia NwrWASHINGTON62021
TriangleIDAHO52014
MerrillOREGON52013
Moses LakeWASHINGTON52021
Iron GateCALIFORNIA42002
Cedar HillIDAHO42014
Warner VallyOREGON42019
Crowder FlatCALIFORNIA32006
Bald Mtn.NEVADA32015
Modoc PointOREGON32018
LeamingtonUTAH31992
Hanford SiteWASHINGTON31996
IngallsCALIFORNIA22001
Crowley LakeCALIFORNIA21988

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