BirdAnalyst
Species · BCR 10 · BBS 2025 Release · 1966–2024

Caspian Tern In Northern Rockies

All regionsNorthern RockiesWetland birds

Caspian Tern in Northern Rockies has declined: down 27% on the route-weighted index since 1988.

-27%Since 1988TrendPercent 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 →
18Routes 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 →
22YearsYears 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 Caspian Tern in Northern Rockies. See the full index history below.

Caspian Tern In Northern Rockies Population Forecast

If the recent trend holds, Caspian Tern in Northern Rockies is projected to stay roughly flat through 2028, near 0.01 (95% range 0.00–0.05). A 5-year backtest shows a typical error of ±134.3%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2028TrendPercent 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 →
0.01Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.0595% 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 →
±134.3%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, Caspian Tern in Northern Rockies is projected to stay roughly flat through 2028, near 0.01 (95% range 0.00–0.05). A 5-year backtest shows a typical error of ±134.3%, with 100% of held-out values landing inside the 95% band.19812028
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 →
20240.020.000.05
20250.020.000.05
20260.010.000.05
20270.010.000.05
20280.010.000.05

Routes In Northern Rockies

Routes recording Caspian Tern in Northern Rockies.
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 →
YellowstoneWYOMING61991
FontenelleWYOMING31994
FeathervilleIDAHO22003
Pablo Res.MONTANA22011
MonumentOREGON21993
CascadeIDAHO11984
KalispellMONTANA12011
BeaverheadMONTANA12018
Red RockMONTANA11981
East Glacier ParkMONTANA12019
Hebgen LakeMONTANA12023
SpartaOREGON11996
Neponset ResUTAH12011
Saleratus CrUTAH12009
Colter BayWYOMING11989
Fiddler LkWYOMING12023
Rock RiverWYOMING11996
HarmonyWYOMING11989

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