BirdAnalyst
Species · Michigan · BBS 2025 Release · 1966–2024

Caspian Tern Population Trend in Michigan

All statesWetland birds

Caspian Tern in Michigan has declined: down 33% on the route-weighted index since 1983.

-33%Since 1983TrendPercent 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 →
14Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
18YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Caspian Tern Trends in MichiganNotable 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 Michigan. See the full index history below.

Caspian Tern Population Forecast in Michigan

If the recent trend holds, Caspian Tern in Michigan is projected to stay roughly flat through 2023, near 0.03 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±50.6%, with 80% of held-out values landing inside the 95% band.

n/aChange by 2023TrendPercent 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 →
0.03Projected 2023 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.0995% 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 →
±50.6%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 →
19732023
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 →
20190.030.000.09
20200.030.000.09
20210.030.000.09
20220.030.000.09
20230.030.000.09

Caspian Tern Survey Routes in Michigan

Routes recording Caspian Tern in Michigan.
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 →
Seney Nwr320092002
Galesburg219731973
No Bradley220122012
Pleasant Valley 2220042004
Adrian220172015
Herman119841983
Remus120072007
Hartland119931993
Mayfield120142014
Riggsville120181981
Walloon Lake 2120072007
Big Blue Lk120132008
Gilchrist120102009
Pleasant Val119941994

Caspian Tern Population Trend in Other States

alabamaalaskacaliforniadelawarefloridaidahoillinoisindianalouisianamarylandminnesotamontananevadanorth-carolinanorth-dakotaoregonsouth-carolinatexasutahvermontvirginiawashingtonwisconsinwyoming

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