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

Black Tern In Great Basin

All regionsGreat BasinWetland birds

Black Tern in Great Basin has collapsed: down 92% on the route-weighted index since 1970.

-92%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 →
41Routes 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 →

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 →

Black Tern has collapsed in Great Basin: down 92% on the route-weighted index since 1970.

Black Tern In Great Basin Population Forecast

If the recent trend holds, Black Tern in Great Basin is projected to fall about 19% by 2029 — from 0.12 in 2024 to a central estimate of 0.10 (95% range 0.00–0.71). A 5-year backtest shows a typical error of ±318.7%, with 100% of held-out values landing inside the 95% band.

-19%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 →
0.10Projected 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 →
0.00–0.7195% 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 →
±318.7%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, Black Tern in Great Basin is projected to fall about 19% by 2029 — from 0.12 in 2024 to a central estimate of 0.10 (95% range 0.00–0.71). A 5-year backtest shows a typical error of ±318.7%, 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 →
20250.130.000.74
20260.120.000.73
20270.110.000.72
20280.110.000.72
20290.100.000.71

Routes In Great Basin

Routes recording Black 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 →
Warner VallyOREGON352007
Catlow RimOREGON202016
Fish LakeOREGON172024
Clear Lk ResCALIFORNIA132004
Blizzard GapOREGON122005
BlyOREGON102001
Bald Mtn.NEVADA82013
ChinchaloOREGON72021
HenryIDAHO61978
DorrisCALIFORNIA52017
Barnes ValOREGON51987
Harney LakeOREGON42003
MaldenWASHINGTON42012
Turnbull NwrWASHINGTON42021
Crowley LakeCALIFORNIA31982
Crowder FlatCALIFORNIA32019
MadelineCALIFORNIA32022
BrewsterWASHINGTON32000
RavendaleCALIFORNIA21979
MacdoelCALIFORNIA22005
SpringfieldIDAHO21973
Dell SpringOREGON21976
Modoc PointOREGON22002
Moses LakeWASHINGTON21990
EwanWASHINGTON22019

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