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Species · Massachusetts · BBS 2025 Release · 1966–2024

Common Tern Population Trend in Massachusetts

All statesWetland birds

Common Tern in Massachusetts has collapsed: down 75% on the route-weighted index since 1969.

-75%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 →
6Routes 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 →
41YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Common Tern Trends in MassachusettsNotable 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 →

Common Tern has collapsed in Massachusetts: down 75% on the route-weighted index since 1969.

Common Tern Population Forecast in Massachusetts

If the recent trend holds, Common Tern in Massachusetts is projected to fall about 97% by 2029 — from 0.47 in 2024 to a central estimate of 0.01 (95% range 0.00–2.3). A 5-year backtest shows a typical error of ±138.1%, with 100% of held-out values landing inside the 95% band.

-97%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 →
0.01Projected 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 →
0.00–2.395% 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 →
±138.1%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, Common Tern in Massachusetts is projected to fall about 97% by 2029 — from 0.47 in 2024 to a central estimate of 0.01 (95% range 0.00–2.3). A 5-year backtest shows a typical error of ±138.1%, with 100% of held-out values landing inside the 95% band.19662029
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 →
20250.100.002.4
20260.080.002.3
20270.060.002.3
20280.040.002.3
20290.010.002.3

Common Tern Survey Routes in Massachusetts

Routes recording Common Tern in Massachusetts.
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 →
Chilmark6419831969
Gay Head720241996
Newburyport320171968
E Dennis120181969
Wellfleet119971966
Cape Cod Ns119981989

Common Tern Population Trend in Other States

alabamaalaskaconnecticutdelawarefloridaidahoindianalouisianamainemarylandmichiganminnesotamontananew-jerseynew-yorknorth-carolinanorth-dakotaohiorhode-islandsouth-dakotatexasvermontvirginiawashingtonwisconsinwyoming

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