BirdAnalyst
Species · BCR 12 · BBS 2025 Release · 1966–2024

Caspian Tern In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionWetland birds

Caspian Tern in Boreal Hardwood Transition has collapsed: down 90% on the route-weighted index since 1969.

-90%Since 1969TrendPercent 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 →
13Routes 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 →
47YearsYears 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 →

Caspian Tern has collapsed in Boreal Hardwood Transition: down 90% on the route-weighted index since 1969.

Caspian Tern In Boreal Hardwood Transition Population Forecast

If the recent trend holds, Caspian Tern in Boreal Hardwood Transition is projected to stay roughly flat through 2029, near 0.00 (95% range 0.00–0.16). A 5-year backtest shows a typical error of ±75.8%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.00Projected 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 →
0.00–0.1695% 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 →
±75.8%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 Boreal Hardwood Transition is projected to stay roughly flat through 2029, near 0.00 (95% range 0.00–0.16). A 5-year backtest shows a typical error of ±75.8%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.000.000.16
20260.000.000.16
20270.000.000.16
20280.000.000.16
20290.000.000.16

Routes In Boreal Hardwood Transition

Routes recording Caspian Tern in Boreal Hardwood Transition.
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 →
Pine RiverMINNESOTA71986
BackusMINNESOTA61992
Seney NwrMICHIGAN32009
Pleasant Valley 2MICHIGAN22004
HermanMICHIGAN11984
GilchristMICHIGAN12010
Pleasant ValMICHIGAN11994
RiggsvilleMICHIGAN12018
Walloon Lake 2MICHIGAN12007
MayfieldMICHIGAN12014
Mille LacsMINNESOTA11979
NebishMINNESOTA11989
Washington IWISCONSIN12024

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