BirdAnalyst
Species · BCR 23 · BBS 2025 Release · 1966–2024

Forster's Tern In Prairie Hardwood Transition

All regionsPrairie Hardwood TransitionWetland birds

Forster's Tern in Prairie Hardwood Transition has risen sharply: up 70% on the route-weighted index since 1975.

+70%Since 1975TrendPercent 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 →
16Routes 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 →
48YearsYears 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 increasecomputed 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 →

Forster's Tern has risen sharply in Prairie Hardwood Transition: up 70% on the route-weighted index since 1975.

Forster's Tern In Prairie Hardwood Transition Population Forecast

If the recent trend holds, Forster's Tern in Prairie Hardwood Transition is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.21). A 5-year backtest shows a typical error of ±128.1%, 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 →
0.05Projected 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 →
0.00–0.2195% 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 →
±128.1%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 Prairie Hardwood Transition is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.21). A 5-year backtest shows a typical error of ±128.1%, with 100% of held-out values landing inside the 95% band.19722029
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 →
20250.060.000.22
20260.050.000.22
20270.050.000.22
20280.050.000.22
20290.050.000.21

Routes In Prairie Hardwood Transition

Routes recording Forster's Tern in Prairie 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 →
Indiana DuneINDIANA121994
EdwardsMINNESOTA82022
Le CenterMINNESOTA52014
CascoWISCONSIN41989
JuniataMICHIGAN32004
OmroWISCONSIN32001
Rolling PrWISCONSIN32010
New LondonMINNESOTA22008
Sherburne NrMINNESOTA21997
HudsonWISCONSIN21986
BriggsvilleWISCONSIN22005
MinnetonkaMINNESOTA11995
ManawaWISCONSIN12001
PardeevilleWISCONSIN12024
BrownsvilleWISCONSIN12008
Omro 2WISCONSIN12022

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